On Ethereum

Fundamentals

• Ethereum Wiki (Ethereum Old Wiki)

• Ethereum White Paper : A Next-Generation Smart Contract and Decentralized Application Platform
• Ethereum Design Rationale
• Ethereum Yello Pager
• Ethereum Beige Paper
• Differences Between a White Paper, Yellow Paper, and Beige Paper (Aug 2, 2018)
• Learn about Ethereum
• Developer Resources
• Ethereum 101
• Ethereum Developer Tools List
• Ethereum Development Tutorial
• A Definitive List of Ethereum Developer Tools (Feb 12, 2019)
• Mastering Ethereum (Andreas M. Antonopoulos, Gavin Wood)
• Ethereum Under the Hood
  • RLP Encoding/Decoding, Trie, Hashing, Blocks

• EthHub : a single source for essential Ethereum information.
• Ethereum Builder's Guide
• Awesome Ethereum Virtual Machine
• Ethereum Homestead Documentation
  • the reference documentation accompanying the Homestead release of the Ethereum project.
• Ethereum Frontier Guide
• Awesome Ethereum Security
• Owesome OpenZeppelin : Blockchain educational resources curated by the OpenZeppelin team.

• Decipher Media

• Ethereum Wallets
• Use Ethereum Applications
• ETHEREUM FOR PYTHON DEVELOPERS

• Hard Problems in Cryptocurrency: Five Years Later (Nov 22, 2019)
• Enterprise Ethereum Architecture Stack Launched (May 2, 2018)

• Small universal Turing machines
• Trapdoor function
• Discrete logarithm

Specs

• Ethash : PoW algorithm for Ethereum 1.0
• Ethereum NatSpec(Natural Specification) Format
• Ethereum Chain Spec Format
  • Subformat: genesis
• Enode URL format

EIP

• EIPs (Ethereum Improvement Proposals)
  • describe standards for the Ethereum platform, including core protocol specifications, client APIs, and contract standards.
• EIP List

EIP/ERC	Title	Description	Category	Status	Remarks	Related
EIP-20	Token Standard	A standard interface for tokens.	ERC	Final	totalSupply, balanceOf, transfer, transferFrom, approve, ...	ERC-2612
EIP-55	Mixed-case checksum address encoding		ERC	Final
EIP-100	Change difficulty adjustment to target mean block time including uncles	the formula to compute the difficulty of a block	Core	Final
EIP-101	Serenity Currency and Crypto Abstraction	Accounts now have only two fields in their RLP encoding: code and storage	Core	Draft	Ethereum 2.0
EIP-155	Simple replay attack protection	provide a way to send transactions that work on Ethereum without working on ETC or the Morden testnet.	Core	Final
EIP-165	Standard Interface Detection	Creates a standard method to publish and detect what interfaces a smart contract implements.	ERC	Final		ERC-1820
EIP-712	Ethereum typed structured data hashing and signing	a standard for hashing and signing of typed structured data as opposed to just bytestrings.	Interface	Draft	ABI, RLP, keccak256, eth_signTypedData
EIP-721	Non-Fungible Token Standard	A standard interface for non-fungible tokens, also known as deeds.	ERC	Final	supportsInterface(bytes4 _if)
EIP-725	Proxy Account	A standard interface for a simple proxy account.	ERC	Draft	execute(...), getData(bytes32 key), setData(bytes32 key, bytes value)
EIP-777	Token Standard	standard interfaces and behaviors for token contracts.	ERC	Final	operators, send/receive hooks	ERC-1820
EIP-1066	Status Codes	Broadly applicable status codes for smart contracts.	ERC	Draft
EIP-1102	Opt-in account exposure	describes a communication protocol between dapps and Ethereum-enabled DOM environments that allows the Ethereum-enabled DOM environment to choose what information to supply the dapp with and when.	Interface	Draft	eth_requestAccounts
EIP-1155	Multi Token Standard	A standard interface for contracts that manage multiple token types.	ERC	Final
EIP-1193	Ethereum Provider JavaScript API	A JavaScript Ethereum Provider API for consistency across clients and applications.	Interface	Last Call	Provider.request()
EIP-1474	Remote procedure call specification	defines a standard set of remote procedure call methods that an Ethereum node should implement.	Interface	Draft	JSON-RPC, Error Codes, Methods
EIP-1559	Fee market change for ETH 1.0 chain	A transaction pricing mechanism that includes fixed-per-block network fee that is burned and dynamically expands/contracts block sizes to deal with transient congestion.	Core	Review	London hard fork	EIP-2718
EIP 1820	Pseudo-introspection Registry Contract	defines a universal registry smart contract where any address (contract or regular account) can register which interface it supports and which smart contract is responsible for its implementation.	ERC	Final		ERC-820, ERC-165
EIP-2612	permit – 712-signed approvals	A function permit extending ERC-20 which allows for approvals to be made via secp256k1 signatures.	ERC	Draft		ERC-20, ERC-712
EIP-2711	Sponsored, expiring and batch transactions	Creates a new transaction type that supports sponsored transactions (separate gas payer from sender), batch transactions (multiple transactions executed in sequence), and expiring transactions (transactions which are not valid after a certain timestamp)	Core	Draft		EIP-2718
EIP-2718	Typed Transaction Envelope	Defines a new transaction type that is an envelope for future transaction types.	Core	Final	Berlin hard fork
EIP-2771	Secure Protocol for Native Meta Transactions	defines a minimal contract-level protocol that a compliant Recipient contract needs to support in order to be capable of accepting a meta transaction through a compliant Forwarder contract that it trusts to help it identify the address of the Transaction Signer.	ERC	Draft
EIP-3091	Block Explorer API Routes	Standard API Routes for Blockchain explorers	Interface	Draft	/block/{BLOCK_HASH_OR_HEIGHT}, /tx/{TX_HASH}, /address/{ACCOUNT_ADDRESS}, /token/{TOKEN_ADDRESS}

• ERC-1155: The Crypto Item Standard (Jun 25, 2018)
• Can ERC-1155 Replace ERC-20 And 721 As The New Standard (Jun 25, 2018)

• ERC-725 Alliance
  • The home of ERC 725, a proposed standard for blockchain-based identity authored by Fabian Vogelsteller, creator of the ERC 20 standard and Web3.js.

• EIP712 is here: What to expect and how to use it (Sep 19, 2018)

EIP Candidates

ERC	Title	Description	Category	Remarks
EIP 677	transferAndCall Token Standard	Adds a new function to ERC20 token contracts, transferAndCall which can be called to transfer tokens to a contract and then call the contract with the additional data provided.	ERC	ERC 20
EIP 734	Key Manager	A contract for key management of a blockchain proxy account.	ERC	ERC 725
EIP 735	Claim Holder	Describes standard functions for adding, removing and holding of claims.	ERC	ERC 725, ERC 734
EIP 780	Ethereum Claims Registry	Describes a proposal for an Ethereum Claims Registry (ECR) which allows persons, smart contracts, and machines to issue claims about each other, as well as self issued claims.	ERC	ERC 735
EIP 1024	Add web3.eth.encrypt and web3.eth.decrypt functions to JSON-RPC	Proposes a cross-client method for requesting encryption/decryption.	Interface
EIP 1238	Non-transferrable tokens (Badges)	Defines a set of standard APIs allowing the identification of statements (called badges) attributed to a public key, such that different dapps and smart contract can use to filter users or to provide user with different badges different experiences.	ERC
ERC 1400	Security Token Standard	Represents a library of standards for security tokens on Ethereum.	ERC	EIPs/issues/1411
ERC 1404	Simple Restricted Token Standard	An open source standard for security tokens	ERC
ERC-1776	Native Meta Transactions	allows users that simply own ERC20 or ERC777 (ERC1155 could be added too) tokens to perform operations on the ethereum network without needing to own ether themselves by letting a third party, the relayer, the responsibility to execute a transaction on the ethereum network carrying the desired operations	ERC

                               
                            +--- Transferrable ---------- EIP 20
                            |
       +--- Fungible -------+
       |                    |
       |                    +--- Non Transferrable ----- 
       |
   +---+
       |
       |                    +--- Transferable ---------- EIP 721
       |                    |
       +--- Non Fungible ---+
                            |
                            +--- Non Transferrable ----- ERC 1238, ERC 735

Concepts

• Ether
  • 1 wei = 10^-18 ether
  • 1 Gwei (shannon) = 10⁹ wei = 10^-9 ether

• Account Types, Gas, and Transactions
  • Externally Owned Account, Contract Account, Transaction, Message, Gas
• What is coinbase? (Apr 16 '16)
• The address of that contract is not the zero address but an address derived from the sender and its number of transactions sent (the “nonce”).
• The gas price is a value set by the creator of the transaction, who has to pay gas_price * gas up front from the sending account. If some gas is left after the execution, it is refunded to the creator in the same way.
• The Ethereum Virtual Machine has three areas where it can store data- storage, memory and the stack

• Mining
• How to Mine Ethereum.
  • Once you’ve successfully mined a block, you are entitled to receive a three ETH reward. Along with the reward, miners receive fees associated with the transaction.

• Uncle Block (Apr 17, 2018)
  • However, at times, two different miners may generate a block simultaneously.
  • Unlike the Bitcoin network which does not reward for orphan blocks, Ethereum incentivizes uncle block miners.
• What is an uncle/ommer block? (Jan 20 '16)
• What is the exact “longest chain” rule implemented in the Ethereum “Homestead” protocol? (Mar 21 '17)
• Longest Chain – How Are Blockchain Forks Resolved? (June 19, 2018)

• Decentralized Autonomous Organization (DAO)
  • an organization represented by rules encoded as a computer program that is transparent, controlled by shareholders and not influenced by a central government.

Keys and Address

Element	Size			Remarks
	Bits	Bytes	Hex Characters
Private Key	256	32	64	a randomly selected positive integer (represented as a byte array of length 32 in big-endian form) in the range [1, secp256k1n − 1]
Public Key	512	64	128	a byte array of size 64 (formed from the concatenation of two positive integers each < 2 256)
Address	160	20	40	the right most 160-bits of the Keccak hash of the corresponding ECDSA public key.

A(p_r)=B_96...256(KEC(ECDSAPUBKEY(p_r)))

A : address
p_r : private key
KEC : Keccak-256 hash function

• Solidity Tutorial : all about Addresses
• Accounts, Addresses, Public And Private Keys, And Tokens
• Understanding the concept of Private Key, Public Key and Address in Ethereum Blockchain (2017/11/17)
• Location of public and private keys of Ethereum account (Apr 25 '17)
  • The private key is never (or should never be) saved unencrypted on disk. It is generated from the info in the keystore file when the user enters the password.
• how to produce enode from node key? (Oct 21 '17)
  • bootnode -nodekeyhex 59233b25bfa4c214a8713e07a395a5d11478de10f36c6c80ba5369541f73bc44 -writeaddress
• Create full Ethereum wallet, keypair and address (Feb 15, 2017)
• What does v, r, s in eth_getTransactionByHash mean? (May 3 '17)
• Get public key of any ethereum account (Mar 31 '17)
• Can I deploy a contract to an arbitrary address that I choose? (Oct 26 '16)
• Signing and Verifying Ethereum Signatures (Nov. 21, 18)

• Keccak
• SHA-3
• ECDSA: (v, r, s), what is v? (Jul 1 '15)

secp256k1

• Elliptic Curve Cryptography (ECC) (Wikipedia)
• Domain parameters
  • ${\textstyle (p,a,b,G,n,h)}$
  • curve parameters and field size : ${\textstyle y^{2}=x^{3}+ax+b\;({\texttt {mod}}\;p)}$
  • generator (base point) : ${\textstyle G}$ ${\textstyle (G_{x},G_{y})}$
  • order : ${\textstyle n}$
  • cofactor : ${\textstyle h}$

• Elliptic Curve Digital Signature Algorithm (ECDSA) (Wikipedia)
• Elliptic Curve Digital Signature Algorithm (BitCoin Wiki)
• A Tale of Two Curves (Nov 1, 2016)
  • secp256k1, secp256r1(prime256)

• secp256k1
  • the parameters of the elliptic curve used in Bitcoin's public-key cryptography, and is defined in Standards for Efficient Cryptography (SEC) (Certicom Research, http://www.secg.org/sec2-v2.pdf)
• github.com/ethereum/go-ethereum/crypto/secp256k1
  • func CompressPubkey()
  • func DecompressPubkey()
  • func RecoverPubkey()
  • func Sign()
  • func VerifySignature()
• github://ethereum/go-ethereum/crypto/secp256k1/libsecp256k1/include/secp256k1.h

• github://ethereum/eth-keys/blob/v0.3.3/eth_keys/constants.py
  • SECPK1_P, SECPK1_N, SECPK1_A, SECPK1_B, SECPK1_Gx, SECPK1_Gy

• secp256k1 domain parameters

Parameter	Name	Value	Decimal Value	Remarks
P	field size	0xFFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFE FFFFFC2F	115792089237316195423570985008687907852837564279074904382605163141518161494337	2256 - 232 - 977
a	curve parameter	0	0
b	curve parameter	7	7
Gx	generator	0x79BE667E F9DCBBAC 55A06295 CE870B07 029BFCDB 2DCE28D9 59F2815B 16F81798	55066263022277343669578718895168534326250603453777594175500187360389116729240
Gy	generator	0x483ADA77 26A3C465 5DA4FBFC 0E1108A8 FD17B448 A6855419 9C47D08F FB10D4B8	32670510020758816978083085130507043184471273380659243275938904335757337482424
n	order	0xFFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFE BAAEDCE6 AF48A03B BFD25E8C D0364141
h	cofactor	1	1

Account State

Field	Symbol	Description	Remarks
nonce	σ[a]n	A scalar value equal to the number of transactions sent from this address or, in the case of accounts with associated code, the number of contract-creations made by this account.
balance	σ[a]b	A scalar value equal to the number of Wei owned by this address.
storageRoot	σ[a]s	A 256-bit hash of the root node of a Merkle Patricia tree that encodes the storage contents of the account.
codeHash	σ[a]c	The hash of the EVM code of this account—this is the code that gets executed should this address receive a message call.	immutable

• Managing nonces with Nethereum
  • Nonces have two functions: 1- Allowing to choose the order in which transactions will be executed. 2- Avoiding replay attacks.
• Nonce in Ethereum
  • Account nonce, Proof of work nonce

Signing

Elment	Symbol	Property	Remarks
private key	pr	${\textstyle 1\leq p_{r}\leq {\texttt {secp256k1n}}-1}$	a randomly selected positive integer
public key	pu	${\textstyle p_{u}\in \mathbb {B} _{64}\equiv {\texttt {ECDSAPUBKEY}}(p_{r}\in \mathbb {B} _{32})}$
signature	v, r, s	${\textstyle (v\in \mathbb {B} _{1},r\in \mathbb {B} _{32},s\in \mathbb {B} _{32})\equiv {\texttt {ECDSASIGN}}(e\in \mathbb {B} _{32},p_{r}\in \mathbb {B} _{32})}$ ${\textstyle {\texttt {ECDSARECOVER}}(e\in \mathbb {B} _{32},v\in \mathbb {B} _{1},r\in \mathbb {B} _{32},s\in \mathbb {B} _{32})\equiv p_{u}\in \mathbb {B} _{64}}$ ${\textstyle 0\leq r\leq {\texttt {secp256k1n}}}$ ${\textstyle 0\leq s\leq {\begin{cases}{\texttt {secp256k1n}}&{\text{if }}H_{i}<N_{H}\\{\texttt {secp256k1n}}\div 2&{\text{otherwise}}\end{cases}}}$ ${\textstyle v\in {27,28}}$
address	A(pr)	${\textstyle \mathbb {B} _{96...256}({\texttt {KEC}}({\texttt {ECDSAPUBK}}(p_{r})))}$	the right most 160-bits of the Keccak hash of the corresponding ECDSA public key
field size	secp256k1n	115792089237316195423570985008687907852837564279074904382605163141518161494337	2256 - 232 - 977

API	Description	Formula	Remarks
eth_sign(address, message)	calculates an Ethereum specific signature	sign(keccak256("\x19Ethereum Signed Message:\n" + len(message) + message))) -> [v, r, s]	v: 1 Byte, r, s: 32 Bytes
eth_signTransaction(tx)	signs a transaction that can be submitted to the network at a later time using with eth_sendRawTransaction
ecrecover(hash, v, r, s)	recover the address associated with the public key from elliptic curve signature
ECDSA.toEthSignedMessageHash()			OpenZeppelin
ECDSA.recover(signature)			OpenZeppelin

• Use solidity ecrecover with signature calculated with eth_sign
• workflow on signing a string with private key, followed by signature verification with public key (Mar 3 '16)
• Signing and Verifying Messages in Ethereum (FEBRUARY 17, 2018)
• The Magic of Digital Signatures on Ethereum (Oct 9, 2020)
• A Closer Look At Ethereum Signatures (February 16th 2018)

• Transaction signing in practice
  1. Create a transaction data structure, containing 9 fields: nonce, gasPrice, gasLimit, to, value, data, chainID, 0, 0
  2. Produce an RLP-encoded serialized message of the transaction data structure
  3. Compute the Keccak256 hash of this serialized message
  4. Compute the ECDSA signature, signing the hash with the originating EOA’s private key.
  5. Append the ECDSA signature’s computed v, r, and s values to the transaction.

• web3.utils.utf8ToHex function

/**
 * Should be called to get hex representation (prefixed by 0x) of utf8 string
 *
 * @method utf8ToHex
 * @param {String} str
 * @returns {String} hex representation of input string
 */
var utf8ToHex = function(str) {
    str = utf8.encode(str);
    var hex = "";

    // remove \u0000 padding from either side
    str = str.replace(/^(?:\u0000)*/,'');
    str = str.split("").reverse().join("");
    str = str.replace(/^(?:\u0000)*/,'');
    str = str.split("").reverse().join("");

    for(var i = 0; i < str.length; i++) {
        var code = str.charCodeAt(i)
        // if (code !== 0) {
        var n = code.toString(16);
        hex += n.length < 2 ? '0' + n : n;
        // }
    }

    return "0x" + hex;
};

Signing Legacy Transaction

Item	Fomula	Remarks
Transaction (Message)	$L_{s}(T)\equiv (T_{n},T_{p},T_{g},T_{t},T_{v},p,\beta ,(),())$ $p\equiv {\begin{cases}T_{i}&{\text{ }}T_{t}=0\\T_{d}&{\text{ otherwise}}\end{cases}}$
Transaction Hash (Message Hash)	$h(T)\equiv {\texttt {KEC}}(L_{s}(T))$
Signed Transaction	$(T_{w},T_{r},T_{s})\equiv {\texttt {ECDSASIGN}}(h(T),p_{r})$	r = $T_{r}$, s = $T_{s}$

Method	Remarks
org.web3j.tx.RawTransactionManager.sendTransaction()	just delegating
org.web3j.crypto.RawTransaction.createTransaction()	just delegating
org.web3j.crypto.transaction.type.LegacyTransaction.createTransaction()	static factory method
org.web3j.crypto.transaction.type.LegacyTransaction.LegacyTransaction()	constructor, remove hexa prefix for data field
org.web3j.crypto.RawTransaction.RawTransaction()	constructor
org.web3j.tx.RawTransactionManager.signAndSend()
org.web3j.tx.RawTransactionManager.sign()	check chain ID
org.web3j.crypto.TransactionEncoder.signMessage()
org.web3j.crypto.TransactionEncoder.encode()
org.web3j.crypto.Sign.SignatureData()

Multisignature

• Multisignature
• Introduction to Multisig Contracts (Jan 16, 2020)

RLP

• RLP
• eth-lib/rlp.js

Transaction

A transaction (formally, T) is a single cryptographically-signed instruction constructed by an actor externally to the scope of Ethereum.

Field	Symbol	Description	Remarks
nonce	Tn	A scalar value equal to the number of transactions sent by the sender
gasPrice	Tp	A scalar value equal to the number of Wei to be paid per unit of gas for all computation costs incurred as a result of the execution of this transaction
gasLimit	Tg	A scalar value equal to the maximum amount of gas that should be used in executing this transaction. This is paid up-front, before any computation is done and may not be increased
to	Tt	The 160-bit address of the message call’s recipient or, for a contract creation transaction, ∅
value	Tv	A scalar value equal to the number of Wei to be transferred to the message call’s recipient or, in the case of contract creation, as an endowment to the newly created account.
v, r, s	Tw, Tr, Ts	Values corresponding to the signature of the transaction and used to determine the sender of the transaction.
init	Ti	An unlimited size byte array specifying the EVM-code for the account initialisation procedure.	a contract creation transaction only
data	Td	An unlimited size byte array specifying the input data of the message call.	a message call transaction only

• Transaction types
• Life Cycle of an Ethereum Transaction (Dec 27, 2017)

• Transaction signature

Signature = F_sig(F_keccak256(m), k) = (r, s)

m : encoded transaction
k : signer's private key
F_keccak256 : Keccak-256 hash function
F_sig : Signing algorithm

• EIP 758: Subscriptions and filters for completed transactions (Draft)
• Get contract return values from transaction recepts (2 Aug 2018)

• Transactions
• What is the difference between a transaction and a call? (an 30 '16)

• Ethereum Transaction Signing (Legacy)
  • 2 times serialization using RLP : each before and after signing
  • sign hashed message

// https://eips.ethereum.org/EIPS/eip-155

tx = [nonce, gasPrice, gasLimit, to, value, data, chainId, 0, 0]

serialized tx = RLP(tx)     // signing data (data to sign)

signature = (r, s, v) = sign(keccak256(RLP(tx)))

serialized signed tx = RLP([nonce, gasPrice, gasLimit, to, value, data, chainId, r, s])

Transaction Receipt

• web3.eth.getTransactionReceipt

Field	Type	Size	Description	Remarks
blockHash	String	32 Bytes	hash of the block where this transaction was in.
blockNumber	Number		block number where this transaction was in.
transactionHash	String	32 Bytes	hash of the transaction.
transactionIndex	Number		integer of the transactions index position in the block.
from	String	20 Bytes	address of the sender.
to	String	20 Bytes	address of the receiver.	null : a contract creation transaction.
cumulativeGasUsed	Number		total amount of gas used when this transaction was executed in the block.
gasUsed	Number		the amount of gas used by this specific transaction alone.
contractAddress	String		the contract address created, if the transaction was a contract creation, otherwise null.
logs	Array		Array of log objects, which this transaction generated.
status	String		'0x0' indicates transaction failure , '0x1' indicates transaction succeeded.

• Deep dive into Ethereum logs (Jan 4, 2018)

• Log Entry Scheme
  • Contract ABI Spec / Events

Component	Description	Remark
address	the address of the contract (intrinsically provided by Ethereum)
topics[0]	keccak(event-signature)	not generated for anonymous event
topics[n]	abi_encode(event-args[indexed][n - 1])	indexed arguments
data	abi_encode(join(event-args[non-indexed]))	non-indexed arguments

• Some transactions are missing receipt (Nov 15 '17)

Typed Transaction

• EIP-2718: Typed Transaction Envelope

• A new transaction type in Ethereum: introduction to eip-2718 (2021-05-18)
• New Transaction Types on Ethereum (May 7th, 2021)

EIP	Title	Transaction Type	Transaction Payload
EIP-1559	Fee market change for ETH 1.0 chain	0x02	RLP([chainId, nonce, maxPriorityFeePerGas, maxFeePerGas, gasLimit, to, value, data, accessList, signatureYParity, signatureR, signatureS])
EIP-2711	Sponsored, expiring and batch transactions	0x02	RLP([...SenderPayload, ...SenderSignature, ...GasPayerPayload, ...GasPayerSignature])
ERC-1776	Native Meta Transactions

Meta Transaction

• Ethereum Meta Transactions : Our Take (Jan 17, 2020)
  • Meta transactions are a type of transaction which is signed by a given key pair, but is funded by a “relay”. The relay submits the transaction to the network as if they are the sender, and pay the gas fee. The destination contract of the transaction can determine the original user, their intent and can process the contract call accordingly.

• Native Meta Transactions (Dec 1, 2018)
• Ethereum Meta-Transactions 101 (Dec 29, 2020)
• lambda-sensui: uPort Funding Service

• Replay Attack Vulnerability in Ethereum Smart Contracts Introduced by transferProxy() (Aug 19, 2018)

bytes32 h = keccak256(_from,_to,_value,_fee,nonce);
if(_from != ecrecover(h,_v,_r,_s)) revert();

let msg = web3.sha3(_from,_to,_value,_fee,nonce)
let signature = web3.eth.sign(_from, msg)

Block

• How does Ethereum work, anyway? (Sep 27, 2017)
• Ethereum under the hood- Part 7( Blocks )
• Ethereum block architecture (Jan 21 '16)

Block Header

Field	Symbol	Description	Remarks
parentHash	Hp	The Keccak 256-bit hash of the parent block’s header, in its entirety.
ommersHash	Ho	The Keccak 256-bit hash of the ommers list portion of this block.
beneficiary	Hc	The 160-bit address to which all fees collected from the successful mining of this block be transferred.
stateRoot	Hr	The Keccak 256-bit hash of the root node of the state trie, after all transactions are executed and finalisations applied;
transactionsRoot	Ht	The Keccak 256-bit hash of the root node of the trie structure populated with each transaction in the transactions list portion of the block.
receiptsRoot	He	The Keccak 256-bit hash of the root node of the trie structure populated with the receipts of each transaction in the transactions list portion of the block.
logsBloom	Hb	The Bloom filter composed from indexable information (logger address and log topics) contained in each log entry from the receipt of each transaction in the transactions list.
difficulty	Hd	A scalar value corresponding to the difficulty level of this block. This can be calculated from the previous block’s difficulty level and the timestamp.
number	Hi	A scalar value equal to the number of ancestor blocks.	0 for genesis block
gasLimit	Hl	A scalar value equal to the current limit of gas expenditure per block
gasUsed	Hg	A scalar value equal to the total gas used in transactions in this block.
timestamp	Hs	A scalar value equal to the reasonable output of Unix’s time() at this block’s inception.
extraData	Hx	An arbitrary byte array containing data relevant to this block. This must be 32 bytes or fewer.
mixHash	Hm	A 256-bit hash which, combined with the nonce, proves that a sufficient amount of computation has been carried out on this block.
nonce	Hn	A 64-bit value which, combined with the mixhash, proves that a sufficient amount of computation has been carried out on this block.

• ommer (uncle) block
  • The term "ommer" is the preferred gender-neutral term for the sibling of a parent block, but this is also sometimes referred to as an "uncle".

World State

• Diving into Ethereum’s world state (Feb 11, 2018)
  • There is one, and one only, global state trie in Ethereum.
  • A storage trie is where all of the contract data lives.
  • Each Ethereum account has its own storage trie.
  • Transaction trie — one per block
  • Ethereum’s Rust client Parity uses rocksdb. Whereas Ethereum’s Go, C++ and Python clients all use leveldb.

• Where is the state data stored?(Jan 22 '16)

• State Tree Pruning (June 26, 2015)

Merkle Patricia Tree

• Trie
  • an ordered tree data structure used to store a dynamic set or associative array where the keys are usually strings.
  • Unlike a binary search tree, no node in the tree stores the key associated with that node; instead, its position in the tree defines the key with which it is associated.
• Radix Tree
  • a data structure that represents a space-optimized trie (prefix tree) in which each node that is the only child is merged with its parent.

• Merkle Patricia Tree Specification
• Why Merkle-Patricia Trie has three types of nodes? (Aug 26 '18)

Consensus

• Ethash

• 2²⁵⁶ = difficulty * target
• avg(difficulty / hash-rate) = block-time
  • Difficulty chart, Hash rate chart

def hashimoto(header, nonce, full_size, dataset_lookup):
    n = full_size / HASH_BYTES
    w = MIX_BYTES // WORD_BYTES
    mixhashes = MIX_BYTES / HASH_BYTES
    # combine header+nonce into a 64 byte seed
    s = sha3_512(header + nonce[::-1])
    # start the mix with replicated s
    mix = []
    for _ in range(MIX_BYTES / HASH_BYTES):
        mix.extend(s)
    # mix in random dataset nodes
    for i in range(ACCESSES):
        p = fnv(i ^ s[0], mix[i % w]) % (n // mixhashes) * mixhashes
        newdata = []
        for j in range(MIX_BYTES / HASH_BYTES):
            newdata.extend(dataset_lookup(p + j))
        mix = map(fnv, mix, newdata)
    # compress mix
    cmix = []
    for i in range(0, len(mix), 4):
        cmix.append(fnv(fnv(fnv(mix[i], mix[i+1]), mix[i+2]), mix[i+3]))
    return {
        "mix digest": serialize_hash(cmix),
        "result": serialize_hash(sha3_256(s+cmix))
    }

def hashimoto_light(full_size, cache, header, nonce):
    return hashimoto(header, nonce, full_size, lambda x: calc_dataset_item(cache, x))

def hashimoto_full(full_size, dataset, header, nonce):
    return hashimoto(header, nonce, full_size, lambda x: dataset[x])

def mine(full_size, dataset, header, difficulty):
    # zero-pad target to compare with hash on the same digit
    target = zpad(encode_int(2**256 // difficulty), 64)[::-1]
    from random import randint
    nonce = randint(0, 2**64)
    while hashimoto_full(full_size, dataset, header, nonce) > target:
        nonce = (nonce + 1) % 2**64
    return nonce

• github://ethereum/go-ethereum/consensus/ethash/consensus.go
  • var FrontierBlockReward = big.NewInt(5e+18)
  • var ByzantiumBlockReward = big.NewInt(3e+18)
  • var ConstantinopleBlockReward = big.NewInt(2e+18)
  • var calcDifficultyByzantium = makeDifficultyCalculator(big.NewInt(3000000))
  • var calcDifficultyConstantinople = makeDifficultyCalculator(big.NewInt(5000000))
  • var calcDifficultyEip2384 = makeDifficultyCalculator(big.NewInt(9000000))
  • func makeDifficultyCalculator(bombDelay *big.Int) func(time uint64, parent *types.Header) *big.Int
    • Ethereum difficulty is integer

• What Is Ethereum's "Difficulty Bomb"? (Jun 25, 2019)
• Why are there no leading zeroes in ethereum block hash? (Mar 15 '16)
  • Essentially there's no reason to actually publish the result of the computation, since everyone will need to recompute it to verify, anyways

• JavaScript code snippet to calculate target in hexa with given difficulty
  • > (2n**256n / 24091770185844n).toString(16).padStart(64, '0') // difficulty: 24091770185844

Gas

• What is Gas?
  • If you want to pay less and are lowering the gas limit below the recommended gas limit, then this will not work. Instead, try lowering the gas price.
• Gas and Gas Price
  • transaction gas limit : max amount of gas your willing to use for your transaction, set by you
  • block gas limit : max amount of gas allowed in a block, set by the network
• What is Ethereum Gas?

• What is the cost to store 1KB, 10KB, 100KB worth of data into the ethereum blockchain? (Feb 2 '16)
  • 256 bit(32 Byte) : 20,000 gas, 1 KB(1,024 KByte) : 640,000 gas, 100 KB : 64,000,000 (6.4e7) gas, 1 MB : 6.4e8 gas

• ETH Gas Station

• What is EIP-1559? How Will It Change Ethereum? (June 22, 2021)
  • During periods of high network congestion, the base fee will adjust by 12.5% depending how much demand surpasses the ideal gas limit per block until that demand abates. Instead of a first-price auction, users will have a better sense of how congested the network is by how high the base fee is. If it is too congested, the user can either pay that price or not, like they would buy an item at a store. Or, they submit a lower fee and wait for the price to go down in the future.

Misc

• Hundreds of Millions of Dollars Locked at 0x0 Address and Smart Contracts’ Addresses — How, Why and What to do? (Jan 13 '18)

Call vs Send

Library	API	Description	Remarks
JSON-RPC	eth_call	Executes a new message call immediately without creating a transaction on the block chain.	No signing, 0 gas
	eth_sendTransaction	Creates new message call transaction or a contract creation, if the data field contains code.
	eth_sendRawTransaction	Creates new message call transaction or a contract creation for signed transactions.	single parameter for the signed transaction data.
web3js 1.2	methods.myMethod.call	Will call a “constant” method and execute its smart contract method in the EVM without sending any transaction. Note calling can not alter the smart contract state.	constant function -> view function in Solidity 0.5
	methods.myMethod.send	Will send a transaction to the smart contract and execute its method. Note this can alter the smart contract state.

Typed Structured Data Signing (EIP-712)

• EIP-712: Ethereum typed structured data hashing and signing

• EIP712 is here: What to expect and how to use it (Sep 19, 2018)

Hard Forks

• History and Network Upgrades
• A Short History of Ethereum MAY 13, 2019
• Ethereum Launches (July 30, 2015)

Fork	Date	Block #	Description	Remarks
Olympic	2015-05-09	N/A	The final PoC testnet
Frontier	2015-06-30	0	The 1st official public mainnet	Block Reward, Gas
Homestead	2016-03-14	1,150,000	The 1st planned hard fork	Solidity, Mist wallet
DAO Fork	2016-06-20	1,192,000	To restore $50M stolen in DAO hack	Ethereum Classic
Spurious Dragon	2016-11-22	2,675,000	Simple replay attack protection (EIP-155, Chain ID) EIP 160, EIP 161 Contract code size limit (EIP-170, 24,576)
Metropolis: Byzantium	2017-10-16	4,370,000	Add REVERT and STATICCALL opcode Block Reward Reduction(5ETH -> 3ETH)
Metropolis: Constantinople	2019-02-28	7,280,000	Smart Contract Verification State Channel Block Reward Reduction(3ETH -> 2ETH)
Istanbul	2019-12-07	9,069,000	Zcash interoperability enhancement SNARK and STARK performance enhancement	EIP 1344, EIP 152, EIP 1108, EIP 2028, EIP 2200
Muir Glacier	2020-01-02	9,200,000	Delays the “difficulty bomb” by 4M blocks.
Berlin	2021-04-15	12,244,000	Typed Transaction Envelope (EIP-2718)
London	August 3-5, 2021	12,965,000	Fee market change for ETH 1.0 chain (EIP-1559)

• Ethereum’s Istanbul Hard Fork Is Now Live (Dec 8, 2019)
  • Ethereum has successfully completed the Istanbul hard fork.
• Muir Glacier: Ethereum Hard Forks for Second Time in One Month (Jan 2, 2020)
  • Ethereum has completed its second hard fork in less than 30 days.
• Berlin Hard Fork Is Now Live on Ethereum (Apr 15, 2021)

• A London tour guide: What the EIP-1559 hard fork promises for Ethereum (APR 19, 2021)
• London Mainnet Announcement (July 15, 2021)

EVM

• Getting Deep Into EVM: How Ethereum Works Backstage (August 16th 2018)

Unlike memory, storage is a persistent area and can only be addressed by words. It is a key-value mapping of 2²⁵⁶ slots of 32 bytes each. A contract can neither read nor write to any storage apart from its own.

Solidity will automatically map every defined state variable of your contract to a slot in storage. The strategy is fairly simple — statically sized variables (everything except mappings and dynamic arrays) are laid out contiguously in storage starting from position 0.

For dynamic arrays, this slot (p) stores the length of the array and its data will be located at the slot number that results from hashing p(keccak256(p)). For mappings, this slot is unused and the value corresponding to a key k will be located at keccak256(k,p).

• Getting Deep Into Ethereum: How Data Is Stored In Ethereum? (July 29th 2018)

• Explaining Ethereum Contract ABI & EVM Bytecode (Jul 16, 2019)

JSON RPC APIs

• JSON RPC API (Generic)
• EIP-1474: Remote procedure call specification : defines a standard set of remote procedure call methods that an Ethereum node should implement.

Object	Description	Properties	Remarks
transaction		from, to, gas, gasPrice, value, data, nonce
transaction receipt

JSON-RPC Method	Description	JavaScript API	Python API
web3_clientVersion	the current client version	web3.eth.getNodeInfo()	web3.clientVersion
web3_sha3	Keccak-256 (not the standardized SHA3-256) of the given data.	web3.utils.sha3()	Web3.keccak()
eth_protocolVersion	the current ethereum protocol version	web3.eth.getProtocolVersion()	web3.eth.protocolVersion
eth_chainId	a single string result for an integer value in hexadecimal format, describing the currently configured CHAIN_ID value used for signing replay-protected transactions	web3.eth.getChainId()	web3.eth.chain_id
eth_syncing	an object with data about the sync status or false	web3.eth.isSyncing()	web3.eth.syncing
eth_coinbase	the coinbase address to which mining rewards will go	web3.eth.getCoinbase()	web3.eth.coinbase
eth_mining	whether the node is mining or not	web3.eth.isMining()	web3.eth.mining
eth_hashrate	the number of hashes per second that the node is mining with	web3.eth.getHashrate()	web3.eth.hashrate
eth_gasPrice	the current price per gas in wei	web3.eth.getGasPrice()	web3.eth.gasPrice
eth_accounts	a list of addresses owned by client	web3.eth.getAccounts()	web3.eth.accounts
eth_blockNumber	the number of most recent block	web3.eth.getBlockNumber()	web3.eth.blockNumber
eth_getBalance	the balance of the account of given address	web3.eth.getBalance()	web3.eth.get_balance()
eth_getTransactionCount	the number of transactions sent from an address. (nonce)	web3.eth.getTransactionCount()	web3.eth.getTransactionCount()
eth_getStorageAt	the value from a storage position at a given address.	web3.eth.getStorageAt()	web3.eth.get_storage_at()
eth_getCode	code at a given address	web3.eth.getCode()	web3.eth.getCode()
eth_getBlockTransactionCountByNumber	the number of transactions in a block matching the given block number.	web3.eth.getBlockTransactionCount()	web3.eth.get_block_transaction_count()
eth_sign	calculates an Ethereum specific signature	web3.eth.sign()	web3.eth.sign()
eth_signTransaction	signs a transaction that can be submitted to the network at a later time.	web3.eth.signTransaction()	web3.eth.signTransaction()
eth_sendTransaction	creates new message call transaction or a contract creation	web3.eth.sendTransaction()	web3.eth.sendTransaction()
eth_sendRawTransaction	creates new message call transaction or a contract creation for signed transactions.	web3.eth.sendSignedTransaction()	web3.eth.sendRawTransaction()
eth_call	executes a new message call immediately without creating a transaction on the block chain.	web3.eth.call()	we3.eth.call()
eth_getBlockByNumber	information about a block by block number.	web3.eth.getBlock()	web3.eth.get_block()
eth_getTransactionByBlockNumberAndIndex	information about a transaction by block number and transaction index position.		web3.eth.getTransactionByBlock()
net_version	the current network id	web3.eth.net.getId()	web3.net.version
net_peerCount	number of peers currently connected to the client.	web3.eth.net.getPeerCount()	web3.net.peer_count
net_listening	whether or not client is actively listening for network connections.	web3.eth.net.isListening()	web3.net.listening

• Looking around the local client using JSON RPC API

$ # Get the client coinbase address. (https://github.com/ethereum/wiki/wiki/JSON-RPC#eth_coinbase)
$ curl -sSX POST --data '{"jsonrpc":"2.0","method":"eth_coinbase","params":[],"id":11}' http://127.0.0.1:8545

$ # Get the client version. (https://github.com/ethereum/wiki/wiki/JSON-RPC#web3_clientversion)
$ curl -sSX POST --data '{"jsonrpc":"2.0","method":"web3_clientVersion","params":[],"id":21}' http://127.0.0.1:8545

$ # Get the Ethereum protocol version. (https://github.com/ethereum/wiki/wiki/JSON-RPC#eth_protocolversion)
$ # For more on Ethereum protocol version, refer https://github.com/ethereum/devp2p/blob/master/caps/eth.md
$ curl -sSX POST --data '{"jsonrpc":"2.0","method":"eth_protocolVersion","params":[],"id":31}' http://127.0.0.1:8545

$ # Get the number of peers currently connected to the client. (https://github.com/ethereum/wiki/wiki/JSON-RPC#net_peercount)
$ curl -sSX POST --data '{"jsonrpc":"2.0","method":"net_peerCount","params":[],"id":41}' http://127.0.0.1:8545

$ # Check whether the client is mining or not. (https://github.com/ethereum/wiki/wiki/JSON-RPC#eth_mining)
$ curl -sSX POST --data '{"jsonrpc":"2.0","method":"eth_mining","params":[],"id":51}' http://127.0.0.1:8545

$ # Get a list of addresses owned by client (https://github.com/ethereum/wiki/wiki/JSON-RPC#eth_accounts)
$ curl -sSX POST --data '{"jsonrpc":"2.0","method":"eth_accounts","params":[],"id":61}' http://127.0.0.1:8545

$ # Get the network ID. (https://github.com/ethereum/wiki/wiki/JSON-RPC#net_version)
$ curl -sSX POST --data '{"jsonrpc":"2.0","method":"net_version","params":[],"id":71}' http://127.0.0.1:8545

$ # Get the current price per gas in wei. (https://github.com/ethereum/wiki/wiki/JSON-RPC#eth_gasprice)
$ curl -sSX POST --data '{"jsonrpc":"2.0","method":"eth_gasPrice","params":[],"id":81}' http://127.0.0.1:8545

$ # Get the number of most recent block. (https://github.com/ethereum/wiki/wiki/JSON-RPC#eth_blocknumber)
$ curl -sSX POST --data '{"jsonrpc":"2.0","method":"eth_blockNumber","params":[],"id":91}' http://127.0.0.1:8545

$ # Get the gas limit of the most recent block
$ curl -sSX POST --data '{"jsonrpc":"2.0","method":"eth_getBlockByNumber","params":["latest", false],"id":92}' http://127.0.0.1:8545 | jq .result.gasLimit

$ # Get information about a block by block number. (https://github.com/ethereum/wiki/wiki/JSON-RPC#eth_getblockbynumber)
$ curl -sSX POST --data '{"jsonrpc":"2.0","method":"eth_getBlockByNumber","params":[0, false],"id":101}' http://127.0.0.1:8545 | jq .  # block 0
$ curl -sSX POST --data '{"jsonrpc":"2.0","method":"eth_getBlockByNumber","params":["0x1", false],"id":102}' http://127.0.0.1:8545 | jq .  # block 1
$ curl -sSX POST --data '{"jsonrpc":"2.0","method":"eth_getBlockByNumber","params":[2, false],"id":103}' http://127.0.0.1:8545 | jq .  # block 1

#! /bin/bash

function print_help {
  echo "Executes some basic Ethereum JSON RPC method to check the specified Ethereum client."
  echo ""
  echo "Usage:"
  echo "  $ ${0##*/}  [-h | --help | rpc_addr]"
  echo ""
  echo "If '-h' or '--help' is given, only display this help and quit."
  echo "If rpc_addr is given, execute some basic Ethereum JSON RPC "
  echo "methods to the specified address."
  echo "If no argument is given, excute the same method to local RPC"
  echo "address of 'http://127.0.0.1:8545'."
}

if [ $# -gt 1 ]; then
  echo "Too many parameters. At the most, one parameter is possible"
  echo ""
  print_help
  exit 100
fi

declare rpc_addr='http://127.0.0.1:8545'

if [ $# -eq 1 ]; then
  if [ "$1" == "-h" -o "$1" == "--help" ]; then
    print_help
    exit 0
  fi
  rpc_addr=$1
fi

# check the specified RPC address
curl -sS $rpc_addr
if [ $? -ne 0 ]; then
  echo "Fail to connect to the specified RPC adderss '$rpc_addr'"
  exit 200
fi

echo "Executing some basic JSON RPC methods to '$rpc_addr'"
echo ""

declare -ar titles=(
'the client coinbase address'
'current client version'
'the current ethereum protocol version'
'number of peers currently connected to the client'
'whether or not client is actively mining new blocks'
'a list of addresses owned by client'
'current network ID'
'the current price per gas in wei'
'the number of most recent block'
'about the genesis block'
)

declare -ar data=(
'{"jsonrpc":"2.0","method":"eth_coinbase","params":[],"id":11}'
'{"jsonrpc":"2.0","method":"web3_clientVersion","params":[],"id":21}'
'{"jsonrpc":"2.0","method":"eth_protocolVersion","params":[],"id":31}'
'{"jsonrpc":"2.0","method":"net_peerCount","params":[],"id":41}'
'{"jsonrpc":"2.0","method":"eth_mining","params":[],"id":51}'
'{"jsonrpc":"2.0","method":"eth_accounts","params":[],"id":61}'
'{"jsonrpc":"2.0","method":"net_version","params":[],"id":71}'
'{"jsonrpc":"2.0","method":"eth_gasPrice","params":[],"id":81}'
'{"jsonrpc":"2.0","method":"eth_blockNumber","params":[],"id":91}'
'{"jsonrpc":"2.0","method":"eth_getBlockByNumber","params":["0x0", false],"id":101}'
)

for (( i = 0; i < ${#titles[@]}; i++ )); do

  cmd="curl -sSX POST --data '${data[$i]}' $rpc_addr"

  echo "// ${titles[$i]}"
  echo $cmd
  eval $cmd
  echo -e "\n"
done

• Verifying a confusing result or situation at the most fundamental level using eth_getTransactionByHash and eth_getTransactionReceipt APIs for each transaction concenred

$ # Get information for the specified transaction (result is not included) (https://eth.wiki/json-rpc/API#eth_gettransactionbyhash)
$ curl -sSX POST --data '{"jsonrpc":"2.0","method":"eth_getTransactionReceipt","params":["0x10f612a42b04ace427b0057caf76d7c7446840f419d4b424f117ecb1bd2cb0e8"],"id":201}' http://127.0.0.1:8545

$ # Get the receipt for the specified transaction, which include the result status and logs (https://eth.wiki/json-rpc/API#eth_gettransactionreceipt)
$ curl -sSX POST --data '{"jsonrpc":"2.0","method":"eth_getTransactionByHash","params":["0x10f612a42b04ace427b0057caf76d7c7446840f419d4b424f117ecb1bd2cb0e8"],"id":211}' http://127.0.0.1:8545

• Rinkeby: “replacement transaction underpriced” (Sep 21 '17)

Networks

• Chainlist : list of EVM networks more than 30 networks
• EVM-based Chains

• Running geth
  • Full node on the main Ethereum network, Full node on the Ethereum test network, Operating a private network
• Private network
• The Geth’s saga: setting up Ethereum private network on windows (Sep 25, 2017)
• Setting up private network or local cluster
• Running Ethereum testnet using Geth
• Ethereum testnets
• ethereum-private-network
  • Instructions on how to setup an ethereum private network
• ADDING NODES TO YOUR PRIVATE BLOCKCHAIN
• Genesis block Explanation
• Network ID and chain ID (March 23, 2021)
  • Peer-to-peer communication between nodes uses the network ID, while the transaction signature process uses the chain ID.
• What is a chainID in Ethereum, how is it different than NetworkID, and how is it used? (Jan 26 '18)
  • Subsequent to EIP-155, ETH has a chainID of 1, while ETC has a chainID of 61 (even though they still have the same networkID of 1)

• Ethereum 101 - Part 6 - Mainnet & Testnets
• Ethereum Test network (May 15, 2018)
• Comparison of the different TestNets (Sep 25 '17)

Network	Chain	Chain ID	Network ID	Consensus	Avg. Block Time	Faucet	Explorer	GitHub	Remark
Ethereum Mainnet	ETH	1	1	PoW
Ethereum Classic Mainnet	ETC	61	1	PoW
Ropsten	ETH	3	3	PoW	30 sec.	https://faucet.ropsten.be/	https://ropsten.etherscan.io/	https://github.com/ethereum/ropsten
Rinkeby	ETH	4	4	PoA	15 sec.	https://faucet.rinkeby.io/	https://www.rinkeby.io/#explorer
Kovan	ETH	42	42	PoA	4 sec.	https://faucet.kovan.network/ https://ethdrop.dev/	https://kovan.etherscan.io/	https://github.com/kovan-testnet
Görli	ETH	5	5	PoA	15 sec.		https://goerli.etherscan.io/	https://github.com/goerli/testnet
Binance Smart Chain Mainnet	BSC	56	56				https://bscscan.com
Binance Smart Chain Testnet	BSC	97	97			https://testnet.binance.org/faucet-smart	https://testnet.bscscan.com

Faucets

Chain	Faucet	Amount	Rermaks
Rinkeby	https://faucet.rinkeby.io/	3 ETH/8 hours, 18.75 ETH/3 days	Require Tweet or Facebook account
	https://faucets.chain.link/rinkeby	0.1 ETH
	https://rinkeby.faucet.epirus.io/	0.2 ETH
	https://rinkeby-faucet.com/

Statistics

Ehtereum Mainnet

• Etherscan > Ethereum Charts & Statistics
• Etherscan > Top Statistics

• Ethstats
• Ethereum Mainnet Statistics
  • Clients, Countries, Sync Status, OS, Network Type

Topic	Charts and Tables	Remarks
Performance	Average Block Time Chart
Mining Difficulty	Etherscan / Ethereum Network Difficulty Chart
	Ethereum Difficulty Chart
Data Size	Full Node Data Size Chart
	Archive Node Data Size Chart
	Average Block Size Chart

• Explorer-as-a-Service (EaaS)

Milestone Blocks

Block #	Hash	Date	Difficulty	Block Reward	Fee Reward	Transactions
10,000,000	0xaa20f7bde5be60603f11a45fc4923aab7552be775403fc00c2e6b805e6297dbe	2020-05-04		2	0.07667	103
9,500,000	0xfd233684d9cbabc563ccc5c3b316ab1f3a22c46cb1495777264f191f5fb96115	2020-02-17	2,230,523,668,588,724	2	0.04033	33
9,000,000	0x388f34dd94b899f65bbd23006ee93d61434a2f2a57053c9870466d8e142960e3	2019-11-26	2,573,664,196,528,490	2	0.14161	95
8,000,000	0x4e454b49dc8a2e2a229e0ce911e9fd4d2aa647de4cf6e0df40cf71bff7283330	2019-06-21	2,037,888,242,889,388	2	0.09102	168
7,000,000	0x17aa411843cb100e57126e911f51f295f5ddb7e9a3bd25e708990534a828c4b7	2019-01-03	2,553,711,764,445,236	3	0.01631	38
6,000,000	0xbe847be2bceb74e660daf96b3f0669d58f59dc9101715689a00ef864a5408f43	2018-07-21	3,483,739,548,912,554	3	0.17281	101
3,000,000	0xee396a86beaade9d6057b72a92b7bf5b40be4997745b437857469557b562a7c3	2017-01-16	103,975,266,902,792	5	0.00851	6
2,000,000	0xc0f4906fea23cf6f3cce98cb44e8e1449e455b28d684dfa9ff65426495584de6	2016-08-03	49,824,742,724,615	5	0.00063	1
1	0x88e96d4537bea4d9c05d12549907b32561d3bf31f45aae734cdc119f13406cb6	2015-07-31	17,171,480,576	5	0	0

Famous Contracts

Service	Contract	Network	Address	Remarks
Uniswap V2	Router	Rinkeby	0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D
ChainLink	Token	Rinkeby	0x01BE23585060835E02B77ef475b0Cc51aA1e0709	ERC-20
		Kovan	0xa36085F69e2889c224210F603D836748e7dC0088	ERC-20

Layer 2

Layer 2 is a collective term for solutions designed to help scale your application by handling transactions off the Ethereum mainnet (layer 1), while taking advantage of the robust decentralized security model of mainnet.

• Scaling (May 26, 2021)
• Layer 2 Rollups (May 26, 2021)

• The Layer 2 Wars Heat Up (Apr 27 2021)
• Layer 2 Won’t Save Ethereum (Apr 28 2021)
• Comparing Layer-2 Ethereum Scaling Solutions (Mar 22, 2021)
• A Beginner’s Guide to Ethereum Scaling Solutions (2021)

Solution	Type	Description	Remarks
OMG Network (a.k.a OmiseGo)	Plazma	leverages Layer-2 Plasma architecture to provide high throughput and strong safety guarantees for third parties who wish to build scalable, decentralized payment apps on the Ethereum Network
Polygon	Sidechain	a protocol and a framework for building and connecting Ethereum-compatible blockchain networks
Optimism	Optimistic Roll-up	an EVM-compatible Optimistic Rollup chain designed to be fast, simple, and secure	sources / docs
zkSync	ZK Roll-up	a scaling and privacy engine for Ethereum	sources / docs
StarkEx	ZK Roll-up	a battle-tested L2 scalability engine, deployed on Mainnet since June 2020
Aztec	ZK Roll-up	an open source layer 2 network bringing scalability and privacy too Ethereum	sources / docs

• Plasma: Scalable Autonomous Smart Contracts (Joseph Poon, Vitalik Buterin, August 11, 2017)
• Plasma EVM
• What is Polygon Network and MATIC? (Mar 16, 2021)

• How does Optimism's Rollup really work? (Jan 29, 2021)
• zkPorter: a breakthrough in L2 scaling (Apr 13 2021)
• A rollup-centric ethereum roadmap (Oct '20)
  • Optimistic rollups still need to have full nodes
• An Incomplete Guide to Rollups (2021 Jan 05, Vitalik Buterin)
  • Plasma and channels are "full" layer 2 schemes, in that they try to move both data and computation off-chain.

Ethereum 2.0

• Ethereum 2.0 (Serenity) Phases
• Ethereum 2.0 Info
• What’s new in Eth2
• ETH2 for Dummies(Jan 8 2020)
• Ethereum 2.0 Devs Handbook and FAQs
• Ethereum 2.0 Specifications
• ETH 2 Phase 2 WIKI
• Phase 2 Proposal 2

• Proof of Stake FAQ
• Sharding FAQ
• CBC Casper FAQ
• Ewasm Design Overview and Specification

• What you can do for Ethereum 2.0 a.k.a. sharding (June 12th, 2018)
• State of Ethereum Protocol #1 (Aug 29, 2018)
• State of Ethereum Protocol #2: The Beacon Chain (Oct 27, 2018)

• Ethereum 2.0: A Complete Guide. Scaling, Part One (Jun 20, 2019)
  • Plasma Chains, State Channels
• Ethereum 2.0: A Complete Guide. Scaling Ethereum — Part Two: Sharding (Jul 11 2019)
• Ethereum 2.0: A Complete Guide. Casper and the Beacon Chain (Aug 6 2019)
• Two Point Oh: Explaining Validators (02 November 2018)
• Two Point Oh: The Beacon Chain (21 November 2018)

• A Journey Through Phase 2 of Ethereum 2.0
• The Future of Ethereum: A Scaling Roadmap to Casper, Plasma, and Sharding (JANUARY 8, 2019)
• Making Sense of Ethereum’s Layer 2 Scaling Solutions: State Channels, Plasma, and Truebit (Feb 12, 2018)
• 2019 Blockchain Layer 2 Solution Review (February 27th 2019)

Casper

• Casper the Friendly Finality Gadget (Vitalik and Virgil's Paper)
  • Casper the Friendly Finality Gadget v1 (25 Oct 2017)
• Casper The Friendly Finality Gadget (Vitalik's Notes)
• Casper FFG: Consensus Protocol for the Realization of Proof-of-Stake
• Ethereum Casper: A Comprehensive Guide
• Casper FFG Overview (Korean)
• Minimal Slashing Conditions (Mar 2, 2017)
• Cryptocurrencies without Proof of Work
• Convenience link to Casper+Sharding chain v2.1 spec (Jun '18)

• A CBC Casper Tutorial (Dec 5, 2018)

Misc

• The Stateless Client Concept

Wallet

• BIP-32 HD Wallets (Hierarchical Deterministic Wallets)

• Signing Azure Key Vault secp256k1
• What is an Ethereum keystore file? (Dec 11, 2017)

Feature	MetaMask	KaiKas
Mnemonic Support	O
Multiple Mnemonics Support
Initializing without Mnemonic	X
Importing Private Key in Plaintext	O
Exporting Private Key into Keystore File	X

HD Wallet

• Ethereum 201: HD Wallets
• Ethereum Wallet Sample code (Apr 2, 2020)

const { hdkey } = require('ethereumjs-wallet'); // https://www.npmjs.com/package/ethereumjs-wallet
const bip39 = require("bip39"); // https://www.npmjs.com/package/bip39

// https://dev.to/dongri/ethereum-wallet-sample-code-10o2
const mnemonic = '...'; // TODO find sample mnemonic
const parentKey = hdkey.fromMasterSeed(bip39.mnemonicToSeedSync(mnemonic)).derivePath("m/44'/60'/0'/0");

const wallets = [];
for(let i = 0; i < 10; i++){
  wallets.push(parentKey.deriveChild(i).getWallet());
}

console.log(`Mnemonic : ${mnemonic}`);
for(i in wallets){
  console.log(`  Account : ${i}th`)
  console.log(`    Private Key : ${wallets[i].getPrivateKeyString()}`);
  console.log(`    Address     : ${wallets[i].getChecksumAddressString()}`);
}

Token

• ERC-20 Token List (Bloxy)
• ERC-721 Token List (Bloxy)
• Ethereum Tokens Explorer

Explorer	Token Contract Type	Count ('21/10/19)	Remarks
Etherscan	Top ERC-20 Tokens	458,890
	Top ERC-721 Tokens	20,735
	Top ERC-1155 Tokens	3,800 (?)	OpenSea Shared Storefront, Rarible(RARI), parallel(LL), Zapper NFT

ERC-20

• EIP-20: Token Standard

// https://eips.ethereum.org/EIPS/eip-20
// https://github.com/OpenZeppelin/openzeppelin-contracts/blob/v4.3.2/contracts/token/ERC20/

interface IERC20 {

    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);

    function name() external view returns (string); //optional

    function symbol() external view returns (string); //optional
    
    unction decimals() external view returns (uint8); //optional

    function totalSupply() external view returns (uint256);

    function balanceOf(address account) external view returns (uint256);

    function transfer(address recipient, uint256 amount) external returns (bool);

    function transferFrom(address sender, address recipient, uint256 amount) 
			external returns (bool);

    function allowance(address owner, address spender) external view returns (uint256);

    function approve(address spender, uint256 amount) external returns (bool);

}

ERC-721

• EIP-721: Non-Fungible Token Standard

// https://eips.ethereum.org/EIPS/eip-721
// https://github.com/OpenZeppelin/openzeppelin-contracts/blob/v4.3.2/contracts/token/ERC721/

interface ERC721 /* is ERC165 */ {

    event Transfer(address indexed _from, address indexed _to, uint256 indexed _tokenId);
    event Approval(address indexed _owner, address indexed _approved, uint256 indexed _tokenId);
    event ApprovalForAll(address indexed _owner, address indexed _operator, bool _approved);

    function balanceOf(address _owner) external view returns (uint256);

    function ownerOf(uint256 _tokenId) external view returns (address);

    function transferFrom(address _from, address _to, uint256 _tokenId) external payable;

    function safeTransferFrom(address _from, address _to, uint256 _tokenId) external payable;

    function safeTransferFrom(address _from, address _to, uint256 _tokenId, bytes data) external payable;

    function approve(address _approved, uint256 _tokenId) external payable;

    function getApproved(uint256 _tokenId) external view returns (address);

    function setApprovalForAll(address _operator, bool _approved) external;

    function isApprovedForAll(address _owner, address _operator) external view returns (bool);
}

interface ERC165 {
    function supportsInterface(bytes4 interfaceID) external view returns (bool);
}

interface ERC721TokenReceiver {

    function onERC721Received(address _operator, address _from, uint256 _tokenId, bytes _data) external returns(bytes4);
}

interface ERC721Metadata { //optional

    function name() external view returns (string _name);

    function symbol() external view returns (string _symbol);

    function tokenURI(uint256 _tokenId) external view returns (string);
}

interface ERC721Enumerable { //optional

    function totalSupply() external view returns (uint256);

    function tokenByIndex(uint256 _index) external view returns (uint256);

    function tokenOfOwnerByIndex(address _owner, uint256 _index) external view returns (uint256);
}

• OpenSea / Contract-level metadata
  • function contractURI() public view returns (string memory)

ERC-1155

• EIP-1155: Multi Token Standard

// https://eips.ethereum.org/EIPS/eip-1155
// https://github.com/OpenZeppelin/openzeppelin-contracts/tree/v4.3.2/contracts/token/ERC1155

interface ERC1155 /* is ERC165 */ {

    event TransferSingle(address indexed _operator, address indexed _from, address indexed _to, uint256 _typeId, uint256 _value);

    event TransferBatch(address indexed _operator, address indexed _from, address indexed _to, uint256[] _typeId, uint256[] _values);

    event ApprovalForAll(address indexed _owner, address indexed _operator, bool _approved);

    event URI(string _value, uint256 indexed _typeId);

    function safeTransferFrom(address _from, address _to, uint256 _typeId, uint256 _value, bytes calldata _data) external;

    function safeBatchTransferFrom(address _from, address _to, uint256[] calldata _typeIds, uint256[] calldata _values, bytes calldata _data) external;

    function balanceOf(address _owner, uint256 _typeId) external view returns (uint256);

    function balanceOfBatch(address[] calldata _owners, uint256[] calldata _typeIds) external view returns (uint256[] memory);

    function setApprovalForAll(address _operator, bool _approved) external;

    function isApprovedForAll(address _owner, address _operator) external view returns (bool);
}

interface ERC1155TokenReceiver {

    function onERC1155Received(address _operator, address _from, uint256 _tpyeId, uint256 _value, bytes calldata _data) external returns(bytes4);

    function onERC1155BatchReceived(address _operator, address _from, uint256[] calldata _typeIds, uint256[] calldata _values, bytes calldata _data) external returns(bytes4);       
}

interface ERC1155Metadata_URI {

    function uri(uint256 _typeId) external view returns (string memory);
}

Famous Tokens

Token	Symbol	Type	Description	Remarks
ChainLink Token	LINK	ERC-677
Wrapped Ether	WETH	ERC-20

Token	Chain	Contract Address	Faucet	Remarks
LINK	Ethereum Mainnet	0x514910771af9ca656af840dff83e8264ecf986ca
LINK	Ethereum Rinkeby	0x01BE23585060835E02B77ef475b0Cc51aA1e0709	https://faucets.chain.link/rinkeby
LINK	Ethereum Kovan	0xa36085F69e2889c224210F603D836748e7dC0088	https://faucets.chain.link/kovan
LINK	Ethereum Goerli	0x326c977e6efc84e512bb9c30f76e30c160ed06fb
LINK	Binance Smart Chain Mainnet	0x404460c6a5ede2d891e8297795264fde62adbb75
WETH	Ethereum Mainnet	0xc02aaa39b223fe8d0a0e5c4f27ead9083c756cc2
WETH	Ethereum Rinkeby	0xc778417e063141139fce010982780140aa0cd5ab

Cross Chain

• A Brief History of Cross-Chain: From Asset Bridge to Interoperability (Jul 13, 2021)
• History of “Cross-chain” and “Bridge”. What is the difference between the bridges at Orbiter Finance? (6月 22, 2021)
  • CEX and Notary scheme, Lightning Network and Hash-locking, Polkadot Relaychain, Sidechain bridges, Bridges for Layer 2 scaling

Token Bridge

Bridge	Description	Documentation	Remarks
POA Bridge Smart Contracts		https://docs.tokenbridge.net/
RSK <-> ETH Token Bridge		https://developers.rsk.co/tools/tokenbridge/
Cross Bridge V1	a trustless peg-in/peg-out bridge that allows users to easily hop between Ethereum (ERC20) and Binance Smart Chain (BEP20).	https://hotcross.com/bridge
Cross Bridge V2	allows end users to security transfer ERC20 tokens from the Ethereum network to the Binance Smart Chain (BSC) and vice versa.	https://hotcross.com/bridge2

• Token Bridge - Crossing ERC20 Tokens between RSK & Ethereum (October 7th 2020)
• Wormhole Releases Solana and Ethereum NFT Bridge — A Bi-Directional Highway for Blockchain Collectibles (Sep 23, 2021)

DAO

• DAO

DAOs are an effective and safe way to work with like-minded folks around the globe.

The backbone of a DAO is its smart contract. The contract defines the rules of the organisation and holds the group's treasury.

DAO	Description	Contracts	Remarks
MakerDAO		https://github.com/makerdao
Moloch DAO		https://github.com/MolochVentures/moloch
DAOhaus	DAOhaus is a no-code platform for launching and running DAOs.		Moloch DAO based
Aragon	Aragon is a suite of applications and services that enable new forms of global communities.

• DAO Explorer

Oracle

• ChainLink Whitepaper - A Decentralized Oracle Network
• ChainLink and Its 4 Main Use Cases (Nov 26, 2018)

• Breaking Down Mixicles and Their Potential to Unlock Enterprise Demand for DeFi Applications On Public Blockchains (4 OCTOBER 2019)

ZKP

• Zero-Knowledge Proof Cryptography: A Gateway to Enterprise Blockchain Adoption (Sep 30, 2019)
• New Zero Knowledge Proof Services Provide Complete Transaction Privacy (Sep 15, 2019)
  • Zether protocol allows ethereum accounts holding ERC20 token balances to fund Zether accounts and obtain ZTH tokens in exchange. Transfer of ZTH tokens among the Zether accounts are conducted with zero knowledge proofs, thus concealing the balances, transfer amount as well as the identity of the trading parties.
  • You can seamlessly transition from executing asset transfers with ERC20/721 tokens, which leak data on the blockchain, to privacy-preserving asset transfers that leverage zero-knowledge proof cryptography, keeping sensitive transactional data off the blockchain.

• Zcash vs Monero - The Complete Guide (January 05, 2021)
• Anatomy of A Zcash Transaction (November 23, 2016)
• Securing a Blockchain with a Noninteractive Zero-Knowledge Proof (MARCH 14, 2019)

Zether

• Zero Knowledge Token Transfer Service: A Tech Overview (Sep 17, 2019)
• Zether: Towards Privacy in a Smart Contract World

AMM

• What Is an Automated Market Maker?
  • Human Market Maker vs. Automated Market Maker
  • Order Book vs. Liquidity Pools
  • On AMM-based decentralized exchanges, the traditional order book is replaced by liquidity pools that are pre-funded on-chain for both assets of the trading pair.
  • One decentralized exchange that has implemented an AMM is Uniswap.
• What Is an Automated Market Maker (AMM)? (Binance Academy)

Protocol	Description	Sources	Remarks
Uniswap		https://github.com/Uniswap
Curve	an exchange liquidity pool on Ethereum designed for: extremely efficient stablecoin trading, low risk, supplemental fee income for liquidity providers, without an opportunity cost.	https://github.com/curvefi
PancakeSwap	The #1 AMM and yield farm on Binance Smart Chain.	https://github.com/pancakeswap

EEA

• Enterprise Ethereum Alliance Off-Chain Trusted Compute Specification v1.1 (07 July 2021)

misc

• Example genesis.json

Programming

• A Gentle Introduction to Ethereum Programming, Part 1 (Nov 15, 2017)
• A Gentle Introduction to Ethereum Programming, Part 2 (Nov 17, 2017)
• A Gentle Introduction to Ethereum Programming, Part 3 (Jan 13, 2018)
• How can I get the data of the latest 10 blocks via web3.js? (Feb 25 '16)
  • web3.eth.getBlock(web3.eth.blockNumber - i)

HTLC

• Hashed Timelock Contract (HTLC) (January 14, 2016)
• Lightning Networks Part II: Hashed Timelock Contracts (HTLCs) (April 1, 2015)
• An Introductory Guide to Hashed TimeLock Contracts (April 1, 2019)
• ERC-1630 Hashed Time-Locked Contracts
• Enabling Cross-Border High Value Transfer Using Distributed Ledger Technologies
  • HTLC sequence flow (18page)

Services

• a Block Explorer and Analytics Platform for Ethereum
• ETH GAS STATION

Hackings

• Parity Multisig Hacked. Again (Nov 8, 2017)
  • About $300M is frozen and (probably) lost forever.

Recommendations

• 5 Essential Ethereum Dapp Tools
• 11 Best Ethereum Development Tools to Grow Your Stack (Feb 25, 2017)

Solidity

• https://github.com/ethereum/solidity
• Desc. : a contract-oriented, high-level language for implementing smart contracts
• License : GPL v3.0
• Sources : https://github.com/ethereum/solidity/

References

• Solidity (on Wikipedia)
  • an object-oriented programming language for writing smart contracts.

• Solidity v0.6.x official documentation

Data types	Address	Array
Contracts	Functions	Structs
Inheritance	Interfaces	Libraries
Units / Global Variables	Block / Transaction	Time Units
Pragmas	Cheatsheet

• Solidity v0.6.0 Breaking Changes
  • Function overriding should be explicit. - virtual, override keywords
  • Array's length property become immutable.
  • Abstract contract should be explicit. - abstract keyword
  • State variable shadowing become disallowed.

• Solidity v0.5.x official documentation

Data types	Address	Array
Contracts	Functions	Structs
Inheritance	Interfaces	Libraries
Units / Global Variables	Block / Transaction	Time Units
Pragmas	Cheatsheet

• Solidity v0.5.0 Breaking Changes
  • Function visibility (external, public, internal, private) should be explicit.
  • Data location for reference types (struct, array, mapping) should be explicit.
  • Conversion from contract type to address should be explicit. - address(contract).balance
  • Explicit conversion between unrelated contract types are disallowed.
  • Split address type into address type and address payable type.
  • For a contract c, address(c) is address payable iff c has payable fallback function.

• Solidity Compiler

• Standard library (draft)
• Change Log
• Common Patterns
• Ethereum Contract ABI
• Ethereum Virtual Machine Opcodes

• Solidity Grammar in Extended BNF
• Solidity Grammar in BNF for IntelliJ

• Solidity Tutorials
• Solidity Tutorials
• Learn Solidity in Y minutes
• Solidity by Example
• CryptoZombies : an interactive school that teaches you all things technical about blockchains

• Solidity Style Guide
• OpenZeppelin Contracts Design Guidelines
  • Private state variables should have an underscore prefix.
  • Internal and private functions should have an underscore prefix.
  • Interface names should have a capital I prefix.

• How To Learn Solidity: The Ultimate Ethereum Coding Guide
• Writing Smart Contracts with Solidity 0.5 and Above
• Solidity Recommendations

Breaking Changes

Version	Category	Change	Remark
0.8	Arithmetic Operation	Arithmetic operations revert on underflow and overflow.
	ABI Coder v2	ABI coder v2 is activated by default.	pragma abicoder
	Opcode	Failing assertions and other internal checks like division by zero or arithmetic overflow do not use the invalid opcode but instead the revert opcode.
	Data-type	The type byte has been removed.	bytes1
	Data-type	Address literals have the type address instead of address payable.	payable()
	Function	Function call options can only be given once.
	Global Function	The global functions log0, log1, log2, log3 and log4 have been removed.	inline assembly
	Global Variable	The global variables tx.origin and msg.sender have the type address instead of address payable.	payable(tx.origin), payable(msg.sender)
	Type Conversion	Explicit conversion into address type always returns a non-payable address type.
0.7	Function	Ether and gas is now specified using a new syntax: x.f{gas: 10000, value: 2 ether}(arg1, arg2).
	Global Variable	The global variable now is deprecated.	block.timestamp
	Data-type	String literals now can only contain printable ASCII characters and this also includes a variety of escape sequences, such as hexadecimal (\xff) and unicode escapes (\u20ac).
	Data-type	Unicode string literals are supported now.	unicode"Hello 😃"
	State Mutability	The state mutability of functions can now be restricted during inheritance.
	Mapping	If a struct or array contains a mapping, it can only be used in storage.
	Mapping	Assignments to structs or arrays in storage does not work if they contain mappings.
	Constructor	Visibility (public / external) is not needed for constructors anymore.	abstract contract
	Function	Disallow virtual for library functions since libraries cannot be inherited from.
	Inheritance	using A for B is NOT inherited.
	Shift Operation	Shifts by signed types are disallowed.
	Variable	The keyword var cannot be used anymore.	(compile-time) parser error

Grammar

Contract = State Variable*, Function*, Function Modifier*, Event*, Struct Type*, Enum Type*

function (<parameter types>) {internal|external} [pure|view|payable] [returns (<return types>)]

• Value Types
  • Value types will always be passed by value

• Reference Types
  • Every reference type, i.e. arrays and structs, has an additional annotation, the “data location”, about where it is stored.
  • All complex types must now give an explicit data location.

• Functions
  • Functions may also return an arbitrary number of values as output.
  • Data location must be memory for return parameter in function

• Constructors
  • Before the constructor code is executed, state variables are initialised to their specified value if you initialise them inline, or zero if you do not.
  • After the constructor has run, the final code of the contract is deployed to the blockchain.
  • The constructors of all the base contracts will be called following the linearization rules explained below.

• Contracts
  • State variables are accessed via their name and not via e.g. `this.owner`. Functions can be accessed directly or through `this.f`, but the latter provides an external view to the function. Especially in the constructor, you should not access functions externally, because the function does not exist yet.

Visibility

• Visibility

Visibility	Description	Remarks
external	Part of the contract interface, which means they can be called from other contracts and via transactions but cannot be called internally	f() does not work, but this.f() works
public	Part of the contract interface and can be either called internally or via messages.
internal	Can only be accessed internally (i.e. from within the current contract or contracts deriving from it)
private	Only visible for the contract they are defined in and not in derived contracts.

Mutability

Mutability	Description	Remarks
pure	Promise not to read from or modify the state.
view	Promise not to modify the state.
nonpayable	Does not accept Ether
payable	Accepts Ether

Types

• Contract ABI Spec > Types
• Types

Category	Types	Remarks
Value Type	Booleans, Integers, Fixed Point Number, Address, Fixed-size Byte Array, Enum
Reference Type	Arrays, Structs, Mappings

• Solidity Types: Mapping, Conversion, Value & Reference Types Explained (Jul 1, 2019)

Value Types

Type	Description	Remarks
int8, int16, int24, ... , int248, int256	signed integer in 8 ~ 256 bits	8 bits step
uint8, uint16, uint24, ... , uint248, uint256	unsigned integer in 8 ~ 256 bits	8 bits step
int	alias for int256	2256 ~ 1077
uint	alias for uint256	2256 ~ 1077
address	Holds a 20 byte value (size of an Ethereum address)
address payable	Same as address, but with the additional members transfer and send
byte1
byte32
enum

Literals

bool b1 = true;   // boolean literal 'true'
bool b2 = false;   // boolean literal 'false'

uint[] arr1 = [uint(1), 2, 3];   // array literal using square bracket

Address Type

• Members of Address Types
• Members of Addresses

Member	Description	Remarks
balance
transfer(uint256 amount)
send(uint256 amount) returns (bool)
call(bytes memory) returns (bool, bytes memory)	issue low-level CALL with the given payload, returns success condition and return data, forwards all available gas, adjustable
delegatecall(bytes memory) returns (bool, bytes memory)	issue low-level DELEGATECALL with the given payload, returns success condition and return data, forwards all available gas, adjustable.
staticcall(bytes memory) returns (bool, bytes memory)	issue low-level STATICCALL with the given payload, returns success condition and return data, forwards all available gas, adjustable.

Reference Types

Type	Description	Remarks
Arrays
bytes
string
Struct
Mappings

Array Type

Category	Variable/Function	Type	Description	Remarks
Array	length	...
	push()			for dynamic storage arrays and bytes, not for string
	pop()			for dynamic storage arrays and bytes, not for string
bytes	concat()

Feature	fixed-size storage array	dynamic-size storage array	fixed-size memory array	dynamic-size memory array
new operator support	X	O	X	O
push(), pop() support	X	O	X	X
initialized with array literal	O	O	O	X
initialized from fixed-size array	O	O	O	X
initialized from dynamic-size array	X		X

Arrays can have a compile-time fixed size, or they can have a dynamic size.

The type of an array of fixed size k and element type T is written as T[k], and an array of dynamic size as T[].

You should use bytes over byte[] because it is cheaper, since byte[] adds 31 padding bytes between the elements.

Memory arrays with dynamic length can be created using the new operator. As opposed to storage arrays, it is not possible to resize memory arrays (e.g. the .push member functions are not available).

Fixed size memory arrays cannot be assigned to dynamically-sized memory arrays.

If you want to initialize dynamically-sized memory arrays, you have to assign the individual elements.

• bytes
  • similar to but cheaper than bytes[]
  • packed tightly in calldata and memory.
  • should be used for arbitrary-length raw byte data

• string
  • equal to bytes
  • not allow length or index access
  • should be used for for arbitrary-length UTF-8 data
  • no built-in manipulation function
  • comparing two strings : keccak256(abi.encodePacked(s1)) == keccak256(abi.encodePacked(s2))
  • concatenating two strings : abi.encodePacked(s1, s2)

• Solidity Tutorial : all about Bytes (Aug 1, 2019·11)

Mapping Types

You can think of mappings as hash tables, which are virtually initialised such that every possible key exists and is mapped to a value whose byte-representation is all zeros, a type’s default value.

... mappings do not have a length or a concept of a key or value being set, and therefore cannot be erased without extra information regarding the assigned keys.

Mappings can only have a data location of storage and thus are allowed for state variables, as storage reference types in functions, or as parameters for library functions. They cannot be used as parameters or return parameters of contract functions that are publicly visible.

• Mappings in Solidity Explained in Under Two Minutes (May 23, 2018)

Data Location

• Data location

Data Location	Features	Lifetime
storage
memory	non-persistent	function call
calldata	non-modifiable, non-persistent

• Currently, reference types comprise structs, arrays and mappings.
• All reference types(array, struct, mapping) must give an explicit data location when used in function parameter, local variable.
• Data location for reference type state variable is always storage implicitly.
• Data location for reference type local variable should be 'storage' or 'memory'.
• Data location for reference type return parameter should be 'memory'.
• Data location for reference type external function parameter should be 'calldata'.

• If you can, try to use calldata as data location because it will avoid copies and also makes sure that the data cannot be modified. Arrays and structs with calldata data location can also be returned from functions, but it is not possible to allocate such types.

Case	Data Location	Remarks
state variable	always storage implicitly
local variable	storage or memory
external function parameter	calldata
return parameter	memory

• Data location and assignment

Assignment	Semantics	Remarks
Assignments between storage and memory	always create an independent copy
Assignments from memory to memory	only create references
Assignments from storage to a local storage variable	only assign a reference
Assignments to state variables	always copy
Assignments to members of local variables of storage struct type	always copy

• Ethereum Solidity: Memory vs Storage & When to Use Them (Mar 18, 2018)
  • storage cannot be newly created in a function. Any storage referenced variable in a function always refers a piece of data pre-allocated on the contract storage (state variable). Any mutation persists after function call.
  • memory can only be newly created in a function. It can either be newly instantiated complex types like array/struct (e.g. via new int[...]) or copied from a storage referenced variable.
  • As references are passed internally through function parameters, remember they default to memory and if the variable was on storage it would create a copy and any modification would not persist.

Usage	storage	memory	calldata	Preferred	Remarks
State variables	O	X	X		forced to storage
Parameters of external functions	X	X	O		forced to calldata
Parameters and returns of functions	O	O	O	memory
Local variables	O	O	O

Literal

Type	Literal	Remarks
address	0xdCad3a6d3569DF655070DEd06cb7A1b2Ccd1D3AF	Hexadecimal literals that are between 39 and 41 digits long

• Address Literals

Default Values (Zero Values)

• default value : initial value whose byte-representation is all zeros
• Scoping and Declarations

Type	Default Value	Remarks
bool	false
uint, int	0
address	address(0)
enum	the first element of the enum
fixed sized array	zero-valued array	an array of the fixed size where all elements are set to initial values
dynamic sized array	empty array	[]
string	empty string	""
mapping	empty mapping
struct	empty struct	a struct value where all members are set to initial values

• What are the initial/zero values for different data types in Solidity? (Feb 22 '18)
• Are there null like thing in solidity (Jun 16 '16)

Special Variables and Functions

• Solidity v0.7.5 Globally Available Variables
• Solidity v0.6.5 Globally Available Variables
• Solidity v0.5.15 Globally Available Variables

Category	Variable/Function	Description	Remarks
Block/Transaction	block.coinbase::address payable	current block miner’s address
	block.number::uint	current block number
	block.timestamp::uint	current block timestamp as seconds since unix epoch
	msg.sender::address payable	sender of the message
	msg.data::bytes	complete calldata
	msg.sig::bytes4	first four bytes of the calldata	function identifier(selector)
	msg.value::uint	number of wei sent with the message
	tx.origin::address payable	sender of the transaction (full call chain)	tx = ∑call
Address/Address Payable	<address>.balance::uint	balance of the address in wei
	<address payable>.transfer()	send given amount of wei to address
	<address payable>.send()	send given amount of wei to address
	<address>.call()	issue low-level CALL with the given payload, returns success condition and return data
	<address>.delegatecall()	issue low-level DELEGATECALL with the given payload, returns success condition and return data
	<address>.staticcall()	issue low-level STATICCALL with the given payload, returns success condition and return data
Contract	this	the current contract	address(this)
	address(contr)	the address of the specified contract instance
	payable(contr)	the address payable of the specified contract instance
Error Handling	assert(bool condition)	causes an invalid opcode and thus state change reversion if the condition is not met - to be used for internal errors.
	require(bool condition)	reverts if the condition is not met - to be used for errors in inputs or external components.

Contract

• A constructor is optional. Only one constructor is allowed.
• If there is no constructor, the contract will assume the default constructor, which is equivalent to constructor() public {}.
• Before the constructor code is executed, state variables are initialised to their specified value if you initialise them inline, or zero if you do not.
• The deployment of the code costs additional gas linear to the length of the code.
• Constructor functions can be either public or internal.
• A constructor set as internal causes the contract to be marked as abstract.

• If the base constructors have arguments, derived contracts need to specify all of them.
• If a derived contract does not specify the arguments to all of its base contracts’ constructors, it will be abstract.

• Contracts may be marked as abstract even though all functions are implemented.
• Abstract contracts can not be instantiated directly.
• Abstract contracts cannot override an implemented virtual function with an unimplemented one.

• We perform an explicit type conversion from `address` to `TokenCreator` and assume that the type of the calling contract is `TokenCreator`, there is no real way to verify that. This does not create a new contract.
  • TokenCreator creator;
  • creator = TokenCreator(msg.sender);
• Explicit conversions to and from address are allowed for integers, integer literals, bytes20 and contract types with the following caveat: The result of a conversion of the form address(x) has the type address payable, if x is of integer or fixed bytes type, a literal or a contract with a receive or payable fallback function. If x is a contract without a receive or payable fallback function, then address(x) will be of type address.

• Functions with the private visibility cannot be virtual.

Library

If library functions are called, their code is executed in the context of the calling contract,... ...

As a library is an isolated piece of source code, it can only access state variables of the calling contract if they are explicitly supplied... ...

Furthermore, internal functions of libraries are visible in all contracts, just as if the library were a base contract.

Error Handling

• Error handling: Assert, Require, Revert and Exceptions

Built-in	Description	Remarks
assert(bool)	causes an invalid opcode and thus state change reversion if the condition is not met - to be used for internal errors.	imply bug, revert operation(0xfd)
require(bool)	reverts if the condition is not met - to be used for errors in inputs or return values from calls to external contracts.	invalid operation (0xfe)

• Solidity performs a revert operation (instruction 0xfd) for a require-style exception and executes an invalid operation (instruction 0xfe) to throw an assert-style exception. In both cases, this causes the EVM to revert all changes made to the state.
• assert-style exceptions consume all gas available to the call, while require-style exceptions do not consume any gas starting from the Metropolis release.

Events

• The Log and its event data is not accessible from within contracts (not even from the contract that created them)

ABI

• Libraries

Package	Class/Function	Description	Remarks
web3.js	web3.eth.abi.encodeFunctionSignature()	Encodes the function name to its ABI signature	encodeFunctionSignature('myMethod(uint256,string)')
	web3.eth.abi.encodeEventSignature()	Encodes the event name to its ABI signature
	web3.eth.abi.encodeParameters()	Encodes a function parameters	encodeParameters(['uint256','string'], ['2345675643', 'Hello!%'])
	web3.eth.abi.decodeParameters()	Decodes ABI encoded parameters to its JavaScript types.
	web3.eth.abi.decodeLog()	Decodes ABI-encoded log data and indexed topic data.
Web3j	org.web3j.abi.TypeEncoder	Ethereum ABI encoding for types.
	org.web3j.abi.TypeDecoder	Ethereum ABI decoding for types.

• Sample Codes

// expecting "0x2fbebd38"
web3.eth.abi.encodeFunctionSignature('foo(uint256)') 

// expecting "0x00000000000000000000000000000000000000000000000000000000002dc6c0"
web3.eth.abi.encodeParameters(['uint256'],[3e6])

// expecting "0x1e15f6d3"
web3.eth.abi.encodeFunctionSignature('bar(uint144)')

// expecting "0x000000000000000000000000000000000000000000000000000000000f32fdc0"
web3.eth.abi.encodeParameters(['uint144'],[255e6])

// expecting "0x6cd57036"
web3.eth.abi.encodeFunctionSignature('foo(uint8[],uint256[])')

// expecting '0x000000000000000000000000000000000000000000000000000000000000004000000000000000000000000000000000000000000000000000000000000000a00000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000000000000007f00000000000000000000000000000000000000000000000000000000000000cb00000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000005f5e100000000000000000000000000000000000000000000000000000000006a18a500' 
web3.eth.abi.encodeParameters(['uint8[]','uint256[]'],[[127,203],[1e8,178e7]])

// expecting "0xd3ca0cb6"
web3.eth.abi.encodeFunctionSignature('bar(uint256[],uint256[])')

// expecting '0x000000000000000000000000000000000000000000000000000000000000004000000000000000000000000000000000000000000000000000000000000000a00000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001b48eb57e0000000000000000000000000000000000000000000000000000000000000000005000000000000000000000000000000000000000000000000000000000000000100000000000000000000000000000000000000000000000000000042d2887600000000000000000000000000000000000000000000000000000000000000001f00000000000000000000000000000000000000000000000000000000013463aa000000000000000000000000000000000000000000000000000000000000007e'
web3.eth.abi.encodeParameters(['uint256[]','uint256[]'],[[0,3e13],[1,287e9,31,20210602,126]])

Readings

Data-type

• What is the zero, empty or null value of a struct? (Feb 2 '16)

• Ethereum Solidity: Memory vs Storage & When to Use Them (Mar 18, 2018)
• Is it possible to have enum as a mapping key type? (Nov 17 '16)

String

• What is the zero value for a string? (Jun 5 '16)
• How to concatenate strings in solidity? (Jan 28 '16)

Structs

• Solidity Tutorial: all about Structs (Aug 1, 2019)
• How can you share a struct definition between contracts in separate files? (Sep 27 '17)
• Returning Struct Array in solidity (Dec 22 '18)
• Solidity tutorial: returning structs from public functions (Jul 12, 2017)
  • In the current version of Solidity (0.4.13, as of this writing), it’s impossible to return a struct from a public function.

Contract

• How to test if a struct state variable is set (Jan 24 '17)

Call

• Ethernaut Lvl 6 Delegation Walkthrough: How to abuse the delicate delegatecall (Aug 22, 2018)
• DelegateCall: Calling Another Contract Function in Solidity (2019/09/01)

• Solidity 0.6.4 and call{value: ...}() instead of call.value()() (21 APRIL 2020)
• Calling the Function of Another Contract in Solidity (Mar 5, 2018)
  • AnotherContract another;
  • constructor(address _at) public{ another = AnotherContract(_at); }

• Getting return values from a solidity transaction(22 Jun 19)

Ether Transfer

• Members of Address Types
  • send(), transfer(), value
  • require(send(amount)) == transfer(amount)

• Secure Ether Transfer
  • Secure transfer of ether from a contract to another address.
  • call.value(amount)(), transfer(amount), send(amount)
• <address>.send vs <address>.transfer best practice usage? (Jul 3 '17)

Assembly

• Solidity Tutorial : all about Assembly (Dec 25, 2019)
• Stack Machines: Fundamentals (Aug 28th, 2013)

Debugging

• Remix / Debugging transactions

Security

• Solidity Security: Comprehensive list of known attack vectors and common anti-patterns (20 October 2018)
• HackPedia: 16 Solidity Hacks/Vulnerabilities, their Fixes and Real World Examples (July 21st 2018)

Guidelines

• Slither Detector Documentation
• Solhint List of Rules
• SWC Registry Smart Contract Weakness Classification

Tools

• Solidity browser based compiler
• Javascript bindings for the solidity compiler
  • compile function
• What are *C*, *E* and *S* properties in message call return object? (Aug 1 '16) : BigNumber

Libraries

• Library Driven Development in Solidity (13 February 2017)
• Proxy Libraries in Solidity (Mar 6, 2017)
• A place for all the ÐApps to live

• List of Solidity libraries in the wild

Patterns

• Solidity Patterns

• Proxy Patterns (APRIL 19, 2018)
• ZeppelinOS Upgrades Pattern
• Solidity DelegateProxy Contracts (May 17, 2018)
• State Machine Pattern

Collections

• awesome-solidity : A curated list of awesome Solidity resources, libraries, tools and more

misc

• Library Driven Development in Solidity
• How do oracle services work under the hood? (Jan 23 '17)
• Solidity Tutorial : all about Comments (Aug 1, 2019)

• Verify ERC20 token on Etherscan that was deployed through Remix: Step by Step Guide
• Inability to verify contract with ABIEncoderV2 on Etherscan (Sep 7 '18)

Best Practices

• OpenZeppelin ERC-20 implementation
• ConsenSys ERC-20 implementation

• Voting
• Ethereum Pet Shop

Category	Title	Description	Package	Remarks
Wallet	Multi-sig contract	Multi-sig, daily-limited account proxy/wallet.
	Gnosis Safe Multisig Wallet
	Argent Wallet Smart Contracts	an Ethereum Smart Contract based mobile wallet.		guarded, recoverable, lockable and upgradable
	BitGo’s Multisig Wallet	Multi-sig contract suitable for use in wallets.		2-of-3 multisig
NFT	CryptoPunks contracts	10,000 unique collectible characters with proof of ownership stored on the Ethereum blockchain.
	Decentraland Land Contracts	Contracts for Decentraland's World
	Decentraland ERC721 Contracts	Contracts for the standard implementation of the ERC721 by Decentraland.	erc721
	Decentraland Collection Contracts	Decentralanad Collection Contracts		Collection V2 contract, Collection V2 Store contract
	Decentraland Marketplace Contracts	Decentralanad Marketplace Contracts
STO	Security Token Standard contracts			ERC-1400
	ConsenSys Codefi Universal Token	a hybrid token standard precisely designed for the use case of tokenized financial assets		ERC-1400
DeFi	MakerDao Multi Collateral Dai contracts
Wallet	Authereum contracts
DEX	Uniswap V2 contracts
	Uniswap V3 core contracts	the core smart contracts for the Uniswap V3 Protocol
	Uniswap V3 periphery contracts	the periphery smart contracts for the Uniswap V3 Protocol
Oracle	Chainlink's Solidity contracts
Bridge	POA Bridge Smart Contracts	implement the logic to relay assets between two EVM-based blockchain networks.
	RSK <-> ETH Token Bridge	allows to move ERC20 tokens from one chain to the other.

Libraries

Fixidity

• https://github.com/CementDAO/Fixidity
• Desc. : A fixed point mathematics library for Solidity
• License : MIT

Tips and Tricks

Typical Codes

// looping array using `length` property
address[] contracts = ...
uint256 n = contracts.length;
for(uint256 i; i < n; i++){
  ...
}


// setting nested mapping value to new struct object
struct Request {
  address owner;
  uint256 at;
}

mapping(address => mapping(uint256 => Request) requests;
requests[tokenContract][assetId] = Request(msg.sender, block.timestamp); // no `new` to create a new struct object


// declaring and initializing dynamic-sized array
uint256 l = ...
address[] memory owners = new address[](l);


// creating local struct array
struct Score {
  address owner;
  uint256 value;
}

uint256 l = ...
Score[] memory srcs = new Score[](l); // new struct array with `new` statement and length parameter

Playing with Arrays

struct Land{
  string name;
  uint256 area; // area in square killometers
}

contract SolidityTest{
   
  function testArrayInitialization() public pure returns(uint256[] memory, bytes[3] memory, string[] memory, Land[] memory){

    //creating arrays without explicit initializing.
    uint256 len = 5;
    uint[] memory scores = new uint[](len); // initialized with default value

    //initializing fixed-size arrays using array literals
    bytes[3] memory rgb = [bytes('RED'), 'GREEN', 'BLUE'];

    //initializing dynamic-size arrays
    //''If you want to initialize dynamically-sized arrays, you have to assign the individual elements'' (from Solidity documentation)
    string[] memory innerPlanets  = new string[](2);
    innerPlanets[0] = 'Mercury';
    innerPlanets[1] = 'Venus';

    Land[] memory continents = new Land[](7);
    continents[0] = Land('Africa', 30_370_000);
    continents[1] = Land('Antarctica', 14_000_000);
    continents[2] = Land('Asia', 44_579_000);
    continents[3] = Land('Europe', 10_180_000);
    continents[4] = Land('North America', 24_709_000);
    continents[5] = Land('South America', 17_840_000);
    continents[6] = Land('Australia', 8_600_000);

      
    return(scores, rgb, innerPlanets, continents);
  }
}

Conversions between bytesM, bytes and string

function testStaticBytesDynamicBytesAndString() public pure returns(bytes[7] memory, bytes32[] memory, bytes[] memory, string[] memory){

  bytes[7] memory rainbow = [bytes('Red'), 'Orange', 'Yellow', 'Green', 'Blue', 'Indigo', 'Viloet'];

  uint256 n = rainbow.length;
  bytes32[] memory colorsInBytes32 = new bytes32[](n);
  for(uint i = 0; i < n; i++){
    colorsInBytes32[i] = bytes32(rainbow[i]); // explicit conversion from `bytes`(dynamic bytes) to `bytes32` (supported from Solidity 0.8.5)
  }

  bytes[] memory colorsInBytes = new bytes[](n);
  string[] memory colorsInString = new string[](n);

  for(uint i = 0; i < n; i++){
    colorsInBytes[i] = bytes.concat(colorsInBytes32[i]);
    colorsInString[i] = string(bytes.concat(colorsInBytes32[i])); // explicit conversion from `bytes32`, via `bytes`, to `string` 
  }

  return (rainbow, colorsInBytes32, colorsInBytes, colorsInString);
}

Clients

top

• Ethereum Mainnet Statistics > Clients

Go Ethereum

• https://geth.ethereum.org/
• Desc. : Official golang implementation of the Ethereum protocol
• License
• Sources : https://github.com/ethereum/go-ethereum

References

• Geth Documentation
• geth Command Line Options

$ geth --help
NAME:
   geth - the go-ethereum command line interface

   Copyright 2013-2021 The go-ethereum Authors

USAGE:
   geth [options] [command] [command options] [arguments...]
   
VERSION:
   1.10.1-stable
   
COMMANDS:
   account                            Manage accounts
   attach                             Start an interactive JavaScript environment (connect to node)
   console                            Start an interactive JavaScript environment
   copydb                             Create a local chain from a target chaindata folder
   db                                 Low level database operations
   dump                               Dump a specific block from storage
   dumpconfig                         Show configuration values
   dumpgenesis                        Dumps genesis block JSON configuration to stdout
   export                             Export blockchain into file
   export-preimages                   Export the preimage database into an RLP stream
   import                             Import a blockchain file
   import-preimages                   Import the preimage database from an RLP stream
   init                               Bootstrap and initialize a new genesis block
   js                                 Execute the specified JavaScript files
   license                            Display license information
   makecache                          Generate ethash verification cache (for testing)
   makedag                            Generate ethash mining DAG (for testing)
   removedb                           Remove blockchain and state databases
   show-deprecated-flags              Show flags that have been deprecated
   snapshot                           A set of commands based on the snapshot
   version                            Print version numbers
   version-check                      Checks (online) whether the current version suffers from any known security vulnerabilities
   wallet                             Manage Ethereum presale wallets
   help, h                            Shows a list of commands or help for one command
   
ETHEREUM OPTIONS:
  --config value                      TOML configuration file
  --datadir value                     Data directory for the databases and keystore (default: "/Users/3rdstage/Library/Ethereum")
  --datadir.ancient value             Data directory for ancient chain segments (default = inside chaindata)
  --datadir.minfreedisk value         Minimum free disk space in MB, once reached triggers auto shut down (default = --cache.gc converted to MB, 0 = disabled)
  --keystore value                    Directory for the keystore (default = inside the datadir)
  --usb                               Enable monitoring and management of USB hardware wallets
  --pcscdpath value                   Path to the smartcard daemon (pcscd) socket file
  --networkid value                   Explicitly set network id (integer)(For testnets: use --ropsten, --rinkeby, --goerli instead) (default: 1)
  --mainnet                           Ethereum mainnet
  --goerli                            Görli network: pre-configured proof-of-authority test network
  --rinkeby                           Rinkeby network: pre-configured proof-of-authority test network
  --yolov3                            YOLOv3 network: pre-configured proof-of-authority shortlived test network.
  --ropsten                           Ropsten network: pre-configured proof-of-work test network
  --syncmode value                    Blockchain sync mode ("fast", "full", "snap" or "light") (default: fast)
  --exitwhensynced                    Exits after block synchronisation completes
  --gcmode value                      Blockchain garbage collection mode ("full", "archive") (default: "full")
  --txlookuplimit value               Number of recent blocks to maintain transactions index for (default = about one year, 0 = entire chain) (default: 2350000)
  --ethstats value                    Reporting URL of a ethstats service (nodename:secret@host:port)
  --identity value                    Custom node name
  --lightkdf                          Reduce key-derivation RAM & CPU usage at some expense of KDF strength
  --whitelist value                   Comma separated block number-to-hash mappings to enforce (<number>=<hash>)
  
LIGHT CLIENT OPTIONS:
  --light.serve value                 Maximum percentage of time allowed for serving LES requests (multi-threaded processing allows values over 100) (default: 0)
  --light.ingress value               Incoming bandwidth limit for serving light clients (kilobytes/sec, 0 = unlimited) (default: 0)
  --light.egress value                Outgoing bandwidth limit for serving light clients (kilobytes/sec, 0 = unlimited) (default: 0)
  --light.maxpeers value              Maximum number of light clients to serve, or light servers to attach to (default: 100)
  --ulc.servers value                 List of trusted ultra-light servers
  --ulc.fraction value                Minimum % of trusted ultra-light servers required to announce a new head (default: 75)
  --ulc.onlyannounce                  Ultra light server sends announcements only
  --light.nopruning                   Disable ancient light chain data pruning
  --light.nosyncserve                 Enables serving light clients before syncing
  
DEVELOPER CHAIN OPTIONS:
  --dev                               Ephemeral proof-of-authority network with a pre-funded developer account, mining enabled
  --dev.period value                  Block period to use in developer mode (0 = mine only if transaction pending) (default: 0)
  
ETHASH OPTIONS:
  --ethash.cachedir value             Directory to store the ethash verification caches (default = inside the datadir)
  --ethash.cachesinmem value          Number of recent ethash caches to keep in memory (16MB each) (default: 2)
  --ethash.cachesondisk value         Number of recent ethash caches to keep on disk (16MB each) (default: 3)
  --ethash.cacheslockmmap             Lock memory maps of recent ethash caches
  --ethash.dagdir value               Directory to store the ethash mining DAGs (default: "${HOME}/Library/Ethash")
  --ethash.dagsinmem value            Number of recent ethash mining DAGs to keep in memory (1+GB each) (default: 1)
  --ethash.dagsondisk value           Number of recent ethash mining DAGs to keep on disk (1+GB each) (default: 2)
  --ethash.dagslockmmap               Lock memory maps for recent ethash mining DAGs
  
TRANSACTION POOL OPTIONS:
  --txpool.locals value               Comma separated accounts to treat as locals (no flush, priority inclusion)
  --txpool.nolocals                   Disables price exemptions for locally submitted transactions
  --txpool.journal value              Disk journal for local transaction to survive node restarts (default: "transactions.rlp")
  --txpool.rejournal value            Time interval to regenerate the local transaction journal (default: 1h0m0s)
  --txpool.pricelimit value           Minimum gas price limit to enforce for acceptance into the pool (default: 1)
  --txpool.pricebump value            Price bump percentage to replace an already existing transaction (default: 10)
  --txpool.accountslots value         Minimum number of executable transaction slots guaranteed per account (default: 16)
  --txpool.globalslots value          Maximum number of executable transaction slots for all accounts (default: 4096)
  --txpool.accountqueue value         Maximum number of non-executable transaction slots permitted per account (default: 64)
  --txpool.globalqueue value          Maximum number of non-executable transaction slots for all accounts (default: 1024)
  --txpool.lifetime value             Maximum amount of time non-executable transaction are queued (default: 3h0m0s)
  
PERFORMANCE TUNING OPTIONS:
  --cache value                       Megabytes of memory allocated to internal caching (default = 4096 mainnet full node, 128 light mode) (default: 1024)
  --cache.database value              Percentage of cache memory allowance to use for database io (default: 50)
  --cache.trie value                  Percentage of cache memory allowance to use for trie caching (default = 15% full mode, 30% archive mode) (default: 15)
  --cache.trie.journal value          Disk journal directory for trie cache to survive node restarts (default: "triecache")
  --cache.trie.rejournal value        Time interval to regenerate the trie cache journal (default: 1h0m0s)
  --cache.gc value                    Percentage of cache memory allowance to use for trie pruning (default = 25% full mode, 0% archive mode) (default: 25)
  --cache.snapshot value              Percentage of cache memory allowance to use for snapshot caching (default = 10% full mode, 20% archive mode) (default: 10)
  --cache.noprefetch                  Disable heuristic state prefetch during block import (less CPU and disk IO, more time waiting for data)
  --cache.preimages                   Enable recording the SHA3/keccak preimages of trie keys
  
ACCOUNT OPTIONS:
  --unlock value                      Comma separated list of accounts to unlock
  --password value                    Password file to use for non-interactive password input
  --signer value                      External signer (url or path to ipc file)
  --allow-insecure-unlock             Allow insecure account unlocking when account-related RPCs are exposed by http
  
API AND CONSOLE OPTIONS:
  --ipcdisable                        Disable the IPC-RPC server
  --ipcpath value                     Filename for IPC socket/pipe within the datadir (explicit paths escape it)
  --http                              Enable the HTTP-RPC server
  --http.addr value                   HTTP-RPC server listening interface (default: "localhost")
  --http.port value                   HTTP-RPC server listening port (default: 8545)
  --http.api value                    API's offered over the HTTP-RPC interface
  --http.rpcprefix value              HTTP path path prefix on which JSON-RPC is served. Use '/' to serve on all paths.
  --http.corsdomain value             Comma separated list of domains from which to accept cross origin requests (browser enforced)
  --http.vhosts value                 Comma separated list of virtual hostnames from which to accept requests (server enforced). Accepts '*' wildcard. (default: "localhost")
  --ws                                Enable the WS-RPC server
  --ws.addr value                     WS-RPC server listening interface (default: "localhost")
  --ws.port value                     WS-RPC server listening port (default: 8546)
  --ws.api value                      API's offered over the WS-RPC interface
  --ws.rpcprefix value                HTTP path prefix on which JSON-RPC is served. Use '/' to serve on all paths.
  --ws.origins value                  Origins from which to accept websockets requests
  --graphql                           Enable GraphQL on the HTTP-RPC server. Note that GraphQL can only be started if an HTTP server is tarted as well.
  --graphql.corsdomain value          Comma separated list of domains from which to accept cross origin requests (browser enforced)
  --graphql.vhosts value              Comma separated list of virtual hostnames from which to accept requests (server enforced). Accepts '*' wildcard. (default: "localhost")
  --rpc.gascap value                  Sets a cap on gas that can be used in eth_call/estimateGas (0=infinite) (default: 25000000)
  --rpc.txfeecap value                Sets a cap on transaction fee (in ether) that can be sent via the RPC APIs (0 = no cap) (default: 1)
  --rpc.allow-unprotected-txs         Allow for unprotected (non EIP155 signed) transactions to be submitted via RPC
  --jspath loadScript                 JavaScript root path for loadScript (default: ".")
  --exec value                        Execute JavaScript statement
  --preload value                     Comma separated list of JavaScript files to preload into the console
  
NETWORKING OPTIONS:
  --bootnodes value                   Comma separated enode URLs for P2P discovery bootstrap
  --discovery.dns value               Sets DNS discovery entry points (use "" to disable DNS)
  --port value                        Network listening port (default: 30303)
  --maxpeers value                    Maximum number of network peers (network disabled if set to 0) (default: 50)
  --maxpendpeers value                Maximum number of pending connection attempts (defaults used if set to 0) (default: 0)
  --nat value                         NAT port mapping mechanism (any|none|upnp|pmp|extip:<IP>) (default: "any")
  --nodiscover                        Disables the peer discovery mechanism (manual peer addition)
  --v5disc                            Enables the experimental RLPx V5 (Topic Discovery) mechanism
  --netrestrict value                 Restricts network communication to the given IP networks (CIDR masks)
  --nodekey value                     P2P node key file
  --nodekeyhex value                  P2P node key as hex (for testing)
  
MINER OPTIONS:
  --mine                              Enable mining
  --miner.threads value               Number of CPU threads to use for mining (default: 0)
  --miner.notify value                Comma separated HTTP URL list to notify of new work packages
  --miner.gasprice value              Minimum gas price for mining a transaction (default: 1000000000)
  --miner.gastarget value             Target gas floor for mined blocks (default: 8000000)
  --miner.gaslimit value              Target gas ceiling for mined blocks (default: 8000000)
  --miner.etherbase value             Public address for block mining rewards (default = first account) (default: "0")
  --miner.extradata value             Block extra data set by the miner (default = client version)
  --miner.recommit value              Time interval to recreate the block being mined (default: 3s)
  --miner.noverify                    Disable remote sealing verification
  
GAS PRICE ORACLE OPTIONS:
  --gpo.blocks value                  Number of recent blocks to check for gas prices (default: 20)
  --gpo.percentile value              Suggested gas price is the given percentile of a set of recent transaction gas prices (default: 60)
  --gpo.maxprice value                Maximum gas price will be recommended by gpo (default: 500000000000)
  
VIRTUAL MACHINE OPTIONS:
  --vmdebug                           Record information useful for VM and contract debugging
  --vm.evm value                      External EVM configuration (default = built-in interpreter)
  --vm.ewasm value                    External ewasm configuration (default = built-in interpreter)
  
LOGGING AND DEBUGGING OPTIONS:
  --fakepow                           Disables proof-of-work verification
  --nocompaction                      Disables db compaction after import
  --verbosity value                   Logging verbosity: 0=silent, 1=error, 2=warn, 3=info, 4=debug, 5=detail (default: 3)
  --log.json                          Format logs with JSON
  --vmodule value                     Per-module verbosity: comma-separated list of <pattern>=<level> (e.g. eth/*=5,p2p=4)
  --backtrace value                   Request a stack trace at a specific logging statement (e.g. "block.go:271")
  --debug                             Prepends log messages with call-site location (file and line number)
  --pprof                             Enable the pprof HTTP server
  --pprof.addr value                  pprof HTTP server listening interface (default: "127.0.0.1")
  --pprof.port value                  pprof HTTP server listening port (default: 6060)
  --pprof.memprofilerate value        Turn on memory profiling with the given rate (default: 524288)
  --pprof.blockprofilerate value      Turn on block profiling with the given rate (default: 0)
  --pprof.cpuprofile value            Write CPU profile to the given file
  --trace value                       Write execution trace to the given file
  
METRICS AND STATS OPTIONS:
  --metrics                           Enable metrics collection and reporting
  --metrics.expensive                 Enable expensive metrics collection and reporting
  --metrics.addr value                Enable stand-alone metrics HTTP server listening interface (default: "127.0.0.1")
  --metrics.port value                Metrics HTTP server listening port (default: 6060)
  --metrics.influxdb                  Enable metrics export/push to an external InfluxDB database
  --metrics.influxdb.endpoint value   InfluxDB API endpoint to report metrics to (default: "http://localhost:8086")
  --metrics.influxdb.database value   InfluxDB database name to push reported metrics to (default: "geth")
  --metrics.influxdb.username value   Username to authorize access to the database (default: "test")
  --metrics.influxdb.password value   Password to authorize access to the database (default: "test")
  --metrics.influxdb.tags value       Comma-separated InfluxDB tags (key/values) attached to all measurements (default: "host=localhost")
  
ALIASED (deprecated) OPTIONS:
  --nousb                             Disables monitoring for and managing USB hardware wallets (deprecated)
  --rpc                               Enable the HTTP-RPC server (deprecated and will be removed June 2021, use --http)
  --rpcaddr value                     HTTP-RPC server listening interface (deprecated and will be removed June 2021, use --http.addr) (default: "localhost")
  --rpcport value                     HTTP-RPC server listening port (deprecated and will be removed June 2021, use --http.port) (default: 8545)
  --rpccorsdomain value               Comma separated list of domains from which to accept cross origin requests (browser enforced) (deprecated and will be removed June 2021, use --http.corsdomain)
  --rpcvhosts value                   Comma separated list of virtual hostnames from which to accept requests (server enforced). Accepts '*' wildcard. (deprecated and will be removed June 2021, use --http.vhosts) (default: "localhost")
  --rpcapi value                      API's offered over the HTTP-RPC interface (deprecated and will be removed June 2021, use --http.api)
  
MISC OPTIONS:
  --snapshot                          Enables snapshot-database mode (default = enable)
  --bloomfilter.size value            Megabytes of memory allocated to bloom-filter for pruning (default: 2048)
  --help, -h                          show help
  --override.berlin value             Manually specify Berlin fork-block, overriding the bundled setting (default: 0)
  

COPYRIGHT:
   Copyright 2013-2021 The go-ethereum Authors

• JavaScript Console
  • $ geth attach ipc:/some/custom/path
  • $ geth attach http://191.168.1.1:8545
  • $ geth attach ws://191.168.1.1:8546

• APIs
  • JSON-RPC API, Console API, Go API

Namespace	Description	Remarks
admin	Gives you access to several non-standard RPC methods, which will allow you to have a fine grained control over your Geth instance, including but not limited to network peer and RPC endpoint management.
clique	Provides access to the state of the clique consensus engine.
debug	Gives you access to several non-standard RPC methods, which will allow you to inspect, debug and set certain debugging flags during runtime.
eth	Provides several extensions to the standard “eth” JSON-RPC namespace.
les	Allows you to manage LES server settings, including client parameters and payment settings for prioritized clients.
miner	Allows you to remote control the node’s mining operation and set various mining specific settings.
personal	Manages private keys in the key store.
txpool	Gives you access to several non-standard RPC methods to inspect the contents of the transaction pool containing all the currently pending transactions as well as the ones queued for future processing.

Readings

• Executing custom JavaScript Snippets through Non-Interactive console (geth --exec) (Jun 24 '16)
  • geth --exec "personal.unlockAccount('$addr', '$passwd', 0)" --verbosity 4 attach http://127.0.0.1:$rpc_port
• Common useful JavaScript snippets for geth (

• Ethereum: Setting Up A Private Blockchain (Apr 22, 2018)
  • To setup and run local standalone geth node.

---

Ethereumj

• https://github.com/ethereum/ethereumj
• Desc. : a pure-Java implementation of the Ethereum protocol
• License : LGPL v3.0

---

Parity Ethereum

• https://www.parity.io/
• Desc. : an Ethereum client, written from the ground-up for correctness-verifiability, modularisation, low-footprint and high-performance
• License : GPL v3.0
• Written in : Rust
• Sources : https://github.com/paritytech/parity

Readings

• Parity official documentation

• What's the difference between the Parity-Ethereum and the Parity client? (Jan 29, 2019)

---

Pantheon

• https://pegasys.tech/
• Desc. : public chain compatible, with a more modular architecture and roadmap to add privacy, permissioning, and new consensus algorithms.
• License : Apache 2.0
• Written in : Java
• Sources
  • https://github.com/PegaSysEng/pantheon

Readings

• Pantheon official documentation
• Scaling Consensus for Enterprise: Explaining the IBFT Algorithm
• Istanbul Byzantine Fault Tolerance

---

Hyperledger Besu

• https://besu.hyperledger.org/en/stable/
• Desc. : an open-source Ethereum client developed under the Apache 2.0 license and written in Java.
• License : Apache 2.0
• Written in : Java
• Sources

Readings

• Besu CLI
• Besu Configuration
• Besu Genesis File
• Besu API Methods
• web3-eea API

• Starting Hyperledger Besu
• Use metrics to monitor node performance

---

Quorum

• https://www.jpmorgan.com/global/Quorum
• Desc. : an Ethereum-based distributed ledger protocol with transaction/contract privacy and new consensus mechanisms
• License : LGPL v3.0 + GPL v3.0
• Written in :
• Sources :
  • https://github.com/jpmorganchase/quorum
  • https://github.com/jpmorganchase/constellation

References

• Quorum wiki
  • Running Quorum

• Provisioning
  • Getting Set Up
  • Running Quorum
  • Installing and running Constellation
  • Constellation Configuration Sample
  • Quorum Examples

Readings

• BUILDING DAPPS FOR QUORUM: PRIVATE ENTERPRISE BLOCKCHAINS
• Raft-based consensus for Ethereum/Quorum
• Gas price issue in Quorum

---

Libraries and Tools

• Hardhat Vs Truffle Vs Remix - Which Is The Best For Blockchain Development? (October 25, 2021)
• Wallets

Wallet	Description	Type	Remarks
MetaMask	A crypto wallet & gateway to blockchain apps	Web, Mobile
WalletConnect	an open protocol for connecting desktop Dapps to mobile Wallets using end-to-end encryption by scanning a QR code.
Fortmatic	allows you to easily integrate your app with the Ethereum blockchain

solc-js

• JavaScript bindings for the Solidity compiler
• Desc. : https://github.com/ethereum/solc-js
• License : MIT License

---

web3.js

• web3.js

• JavaScript API (web3.js) 1.2.4
• JavaScript API (web3.js) 1.0
• JavaScript API (web3.js) 0.2.x.x
• Management APIs

Package	Description	Remarks
web3.eth	Allows you to interact with an Ethereum blockchain and Ethereum smart contracts.
web3.eth.accounts	Contains functions to generate Ethereum accounts and sign transactions and data.
web3.eth.Contract	The object makes it easy to interact with smart contracts on the ethereum blockchain.
web3.utils	Provides utility functions for Ethereum dapps and other web3.js packages.
web3.eth.abi	Let you de- and encode parameters to ABI (Application Binary Interface) for function calls to the EVM.

API	Parameters	Description	Remarks
web3.eth.getNodeInfo		Returns the current client version	web3_clientVersion
web3.eth.getChainId		Returns the chain ID of the current connected node as described in the EIP-695	eth_getChainId
web3.eth.net.getId		Gets the current network ID	net_version
web3.eth.blockNumber		Returns the current block number
web3.eth.getBlock		Returns a block matching the block number or block hash
web3.eth.getAccounts	Function callback	Will return a list of the unlocked accounts in the Web3 wallet or it will return the accounts from the currently connected node
web3.eth.getBalance	String address String|Number defaultBlock Function callback	Get the balance of an address at a given block
web3.eth.getTransactionReceipt		Returns the receipt of a transaction by transaction hash.
web3.eth.call		Executes a message call transaction, which is directly executed in the VM of the node, but never mined into the blockchain.
web3.eth.sendTransaction		Sends a transaction to the network.	transaction object (from, to, value, gas, gasPrice, data, nonce)
web3.eth.sendSignedTransaction	String data	Sends an already signed transaction
web3.eth.sign	String data, String addr	Signs data using a specific account.	account needs to be unlocked
web3.eth.signTransaction	Object tx, String addr	Signs a transaction.	account needs to be unlocked
web3.eth.accounts.hashMessage	String msg	Hashes the given message using keccak256 after UTF-8 HEX decoding and envelop ("\x19Ethereum Signed Message:\n" + msg.length + msg)
web3.eth.accounts.sign	String data, String prvKey	Signs arbitrary data.	"\x19Ethereum Signed Message:\n" + msg.length + msg
web3.eth.accounts.signTransaction	Object tx, String prvKey	Signs an Ethereum transaction with a given private key.
web3.eth.accounts.recover		Recovers the Ethereum address which was used to sign the given data.
web3.eth.accounts.recoverTransaction		Recovers the Ethereum address which was used to sign the given RLP encoded transaction.	The RLP encoded transaction
web3.eth.accounts.privateKeyToAccount	String privateKey	Creates an account object from a private key.	create not an account but an account object
web3.utils.sha3	String string	Calculate the sha3 of the input.	Alias: keccak256
web3.utils.asciiToHex	String string	Transform an ASCII string into a valid bytes4, bytes8 etc	Alias: fromAscii()
web3.utils.utf8ToHex	String string	Returns the HEX representation of a given UTF-8 string.	Alias : stringToHex(), fromUtf8()
web3.eth.abi.encodeFunctionCall	Object jsonInterfacer Array parameters	Encodes a function call using its JSON interface object and given parameters.

web3.utils
  // safely convert any given value (including BigNumber.js instances) into a BN.js instance, 
  // for handling big numbers in JavaScript.
  web3.utils.toBN(String|Number|HEX);

  // calculate the sha3 of the input.
  web3.utils.sha3(String);
  web3.utils.keccack256(String);

  // returns the HEX representation of a given ASCII string.
  web3.utils.asciiToHex(String);
  web3.utils.fromAscii(String); // deprecated

Readings

• Web3 Configuration
  • Setting Authorization header to specify bearer access token is a little bit different between Web3HttpProvider and Web3WsProvider.

• How to get Ethereum Block Gas Limit (May 4, 2018)
  • web3.eth.getBlock("latest").gasLimit
• How do I sign transactions with Web3? (Jun 22, 2018)
  • contract.methods.f(arg, arg2).encodeABI(), web3.eth.accounts.signTransaction(tx, privateKey), web3.eth.sendSignedTransaction(raw)

Sample Codes

Basic Usage

$ truffle console --network ropsten
Warning: Please rename truffle.js to truffle-config.js to ensure Windows compatibility.
truffle(ropsten)> web3.version
'1.2.1'
truffle(ropsten)> web3.eth.getCoinbase()
...
truffle(ropsten)> web3.eth.getCoinbase().then(web3.eth.getBalance).then(v => parseInt(v).toLocaleString())
...
truffle(ropsten)> web3.eth.getNodeInfo()
'Geth/v1.9.9-omnibus-e320ae4c-20191206/linux-amd64/go1.13.4'
truffle(ropsten)> web3.eth.getProtocolVersion()
'0x40'
truffle(ropsten)> web3.eth.net.getPeerCount()
100
truffle(ropsten)> web3.eth.isMining()
false
truffle(ropsten)> web3.eth.getAccounts()
[ ... ]
truffle(ropsten)> web3.eth.getAccounts().then(accts => accts.forEach(acct => web3.eth.getBalance(acct).then(amt => console.log(acct, amt))))
...

truffle(ropsten)> Promise.all(accounts.map(acct => web3.eth.getBalance(acct).then(balance => [acct, balance])))
...
truffle(ropsten)> web3.eth.net.getId()
3
truffle(ropsten)> web3.eth.getGasPrice().then(v => parseInt(v).toLocaleString())
'1,000,000,000'
truffle(ropsten)> web3.eth.getBlock("latest").then(b => parseInt(b.gasLimit).toLocaleString())
'8,000,029'
truffle(ropsten)> web3.eth.getBlockNumber().then(v => v.toLocaleString())
'7,553,661'
truffle(ropsten)> web3.eth.getBlock(0)
{ difficulty: '1048576',
  extraData:
   '0x3535353535353535353535353535353535353535353535353535353535353535',
  gasLimit: '0x1000000',
  gasUsed: '0x0',
  hash:
   '0x41941023680923e0fe4d74a34bdac8141f2540e3ae90623718e47d66d1ca4a2d',
  logsBloom:
   '0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000',
  miner: '0x0000000000000000000000000000000000000000',
  mixHash:
   '0x0000000000000000000000000000000000000000000000000000000000000000',
  nonce: '0x0000000000000042',
  number: 0,
  parentHash:
   '0x0000000000000000000000000000000000000000000000000000000000000000',
  receiptsRoot:
   '0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421',
  sha3Uncles:
   '0x1dcc4de8dec75d7aab85b567b6ccd41ad312451b948a7413f0a142fd40d49347',
  size: 540,
  stateRoot:
   '0x217b0bbcfb72e2d57e28f33cb361b9983513177755dc3f33ce3e7022ed62b77b',
  timestamp: 0,
  totalDifficulty: '1048576',
  transactions: [],
  transactionsRoot:
   '0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421',
  uncles: [] }

Event Subscription

Sample code inside Truffle console to subscribe event using web3.eth.subscribe() function via web socket. The address 0xa36085F69e2889c224210F603D836748e7dC0088 below is an address of ChainLink's token contract at Kovan network.

$ truffle console --network kovan_ws
truffle(kovan_ws)> let options = { address: '0xa36085F69e2889c224210F603D836748e7dC0088' };
undefined
truffle(kovan_ws)> let subscription = web3.eth.subscribe('logs', options, (err, result) => { if(err) console.error(err); });
undefined
truffle(kovan_ws)> subscription.on('data', function(log) { console.log(log); });
...

---

EthereumJS

• https://github.com/ethereumjs
• Desc. : Ethereum Javascript Community
• License :
• Written in : JavaScript

Package	Description	Documentation	API	Remarks
@ethereumjs/common	Resources common to all EthereumJS implementations			chains, hardforks
ethereumjs-util	A collection of utility functions for Ethereum		API	Address, Account, ECDSASignature, BN, rlp
ethereumjs-wallet	A lightweight wallet implementation		API	Wallet class, EthereumHDKey class
@ethereumjs/tx	Implements schema and functions related to Ethereum's transaction		API

---

Ethers

• https://github.com/ethers-io/ethers.js/
• Desc. : A complete Ethereum wallet implementation and utilities in JavaScript (and TypeScript)
• License : MIT
• Written in : JavaScript

• Ethers Getting Started
• Ethers API

---

bitcoinjs

• https://github.com/bitcoinjs
• Desc. : Open source organisation for Bitcoin libraries
• License :
• Written in : JavaScript

Package	Description	Documentation	Remarks
BIP39	JavaScript implementation of Bitcoin BIP39: Mnemonic code for generating deterministic keys		BIP-39

---

Web3j

• https://web3j.io/
• Desc. : a lightweight, highly modular, reactive, type safe Java and Android library for working with Smart Contracts and integrating with clients (nodes) on the Ethereum network
• License : Apache License 2.0
• Written in : Java
• Sources
  • https://github.com/web3j/web3j
  • https://github.com/web3j/quorum
  • https://github.com/web3j/examples

References

• web3j official documentation
• Ethereum for Java Developers

• API Documentation

Version	API
4.5.18	Web3j Core API
	Web3j Crypto API
	Web3j Utils API

• Core APIs

                                               extends
                                            +------------ Ethereum
  JsonRpc2_0Web3j ---------------- Web3j ---|
                     implements             +------------ Web3jRx
                                               extends

Class	Source	API	Remark
public class HttpService extends Service	HttpService.java		HTTP implementation of our services API
org.web3j.protocol.Service	Service.java		Base service implementation
public class JsonRpc2_0Web3j implements Web3j	JsonRpc2_0Web3j.java		JSON-RPC 2.0 factory implementation
interface org.web3j.protocol.Web3j	Web3j.java		extends Ethereum, Web3jRx
interface org.web3j.protocol.core.Ethereum	Ethereum.java		JSON-RPC methods
interface org.web3j.protocol.rx.Web3jRx	Web3jRx.java
interface org.web3j.quorum.Quorum	Quorum.java		extends Web3j
org.web3j.tx.Contract	Contract.java
org.web3j.protocol.core.RemoteCall<T>	RemoteCall.java
org.web3j.protocol.core.methods.request.Transaction	Transaction.java
abstract org.web3j.abi.TypeReference<T extends org.web3j.abi.datatypes.Type>	TypeReference.java
org.web3j.abi.datatypes.Function	Function.java

• ABI Types

  Type<T> ---+--- NumericType implements Type<BigInteger> ---+--- IntType ---+--- Uint ---+--- Uint8
             |                                                |               |            |
             |                                                |               |            +--- Uint16
             |                                                |               |
             |                                                |               +--- Int  ---+--- Int8
             |                                                |                            |
             |                                                |                            +--- Int8
             |                                                |                                      
             |                                                +--- FixedPointType ---+--- Ufixed
             |                                                                       |
             |                                                                       +--- Fixed
             |
             +--- BytesType implements Type<bytes[]> ---+--- Bytes ---+--- Bytes1
             |                                          |             |
             |                                          |             +--- Bytes2

Crypto/Util APIs

Class	Method	Description	Remarks
Keys
	static ECKeyPair createEcKeyPair(SecureRandom random)	Generate Elliptic Curve key pair for a Ethereum account
	static ECKeyPair createEcKeyPair()	Generate Elliptic Curve key pair for a Ethereum account
	static String getAddress(ECKeyPair pair)	address in 40-bytes hexadecimal format.	Without prefix
	static String toChecksumAddress(String address)	Checksum address encoding as per EIP-55.	EIP-55, With '0x' prefix
Sign		Transaction signing logic.
RawTransaction
	static createTransaction createTransaction(...)	create raw transaction object that is not signed	transaction object
TransactionEncoder
	static byte[] signMessage(RawTransaction rawTx, Credentials cred)	sign a raw transaction
Numeric
	static BigInteger toBigInt(String hexValue)	Get integer representation from the hexadecimal representation for private key, public key, or so on
	static String toHexStringNoPrefixZeroPadded(BigInteger value, int size)	Get hexadecimal represenation with prefix `0x` and in the specified length from the integer repesentation for private key, public key, or so on
	static String toHexString(byte[] input)	Get hexadecimal representation of the specified byte array with prefix '0x'
	static String toHexStringNoPrefix(byte[] input)	Get hexadecimal representation fo the specified byte array without prefix
	byte[] hexStringToByteArray(String input)	Convert string in hexdecimal format into byte array after removing prefix `0x` if any

// create Elliptic Curved key pair
ECKeyPair pair = Keys.createEcKeyPair();

// get EIP-55(checksum) address with '0x' prefix from EC key-pair
String addr = Keys.toChecksumAddress(Keys.getAddress(pair));

// or get EIP-55 address with '0x' prefix from public key
add = Keys.toChecksumAddress(Keys.getAddress(pair.getPublicKey());

// get private key in hexadecimal string without any prefix - 64 characters with left zero padding
Numeric.toHexStringNoPrefixZeroPadded(pair.getPrivateKey(), Keys.PRIVATE_KEY_LENGTH_IN_HEX);

// get public key in hexadecimal string without any prefix - 128 characters with left zero padding
Numeric.toHexStringNoPrefixZeroPadded(pair.getPublicKey(), 2 * Keys.PRIVATE_KEY_LENGTH_IN_HEX);

// convert hexadecimal string to integer in 'BigInteger' type
final BigInteger gas = Numeric.toBigInt("0x12e140");

Dependencies

Package	Description	Sources	Remarks
eth-lib	Lightweight Ethereum libraries.	https://github.com/maiavictor/eth-lib
elliptic	Fast elliptic-curve cryptography in a plain javascript implementation.	https://github.com/indutny/elliptic
secp256k1	Provides native bindings to bitcoin-core/secp256k1.	https://github.com/cryptocoinjs/secp256k1-node

Readings

• Deploying and interacting with smart contracts
  • Creation of a smart contract
  • Transacting with a smart contract
  • Querying the state of a smart contract

• Connecting to an Ethereum client with Java, Eclipse and Web3j (20 Jul 19)
• Manage an Ethereum account with Java and Web3j (06 Nov 19)
• Interacting with an Ethereum Smart Contract in Java (27 Jan 20)

• Script To Find Transactions To/From An Account
  • for (var i = startBlockNumber; i <= endBlockNumber; i++)
• Connecting to an Ethereum client with Java, Eclipse and Web3j
• Open or create an account with Web3j
  • WalletUtils.loadCredentials, WalletUtils.loadBip39Credentials
• How to change logging level on org.web3j.protocol.http.HttpService (30 Jul 2018)
  • <logger name="org.web3j.protocol" level="INFO"/>

• Java Code Examples for org.web3j.crypto.ECKeyPair
  • Numeric.toHexStringWithPrefix

Tips and Tricks

Hexbinary, byte array and string

• xsd:hexBinary : Binary contents coded in hexadecimal

import jakarta.xml.bind.DatatypeConverter;
...

  @Test
  public void testHexStringToString() {

    final String hStr = "0x477265656e";
    final byte[] bytes = DatatypeConverter.parseHexBinary(
        StringUtils.removeStart(hStr, "0x")); // will be {71,114,101,101,110}
    final String str = new String(bytes);
    Assertions.assertEquals("Green", str);

    this.logger.info("Hex Binary Representation: '{}'", hStr);
    this.logger.info("Byte Array: {}", ArrayUtils.toString(bytes));
    this.logger.info("String: '{}'", str);


    final String hStr2 = "0x5768697465000000000000000000000000000000000000000000000000000000";
    final byte[] bytes2 = DatatypeConverter.parseHexBinary(
        StringUtils.removeStart(hStr2, "0x"));	// will be {87,104,105,116,101,0,...,0}

    final String str2 = new String(bytes2);	
    Assertions.assertNotEquals("White", str2);
    Assertions.assertEquals(32, str2.length());
    Assertions.assertEquals("White", str2.trim());


    this.logger.info("Hex Binary Representation: {}", hStr2);
    this.logger.info("Byte Array: {}", ArrayUtils.toString(bytes2));
    this.logger.info("String: {}", str2);
  }

---

Web3.py

• https://github.com/ethereum/web3.py
• Desc. : A Python library for interacting with Ethereum, inspired by web3.js.
• License : MPL-2.0 (Mozilla Public License 2.0)
• Written in : Python

Packages

Package	Description	Documentation	Sources	Remarks
Web3.py	A Python library for interacting with Ethereum, inspired by web3.js.	stable latest	https://github.com/ethereum/web3.py
eth-account	Sign Ethereum transactions and messages with local private keys	stable	https://github.com/ethereum/eth-account/
eth-keys	A common API for Ethereum key operations with pluggable backends.		https://github.com/ethereum/eth-keys/
eth-utils	Common utility functions for python code that interacts with Ethereum		https://github.com/ethereum/eth-utils	keccack, ABI utils, Crypto utils, Address utils, ...
eth-typing	Common type annotations for ethereum python packages.	stable	https://github.com/ethereum/eth-typing

API

Class	API	Description	Remarks
web.Web3
	api	the current Web3 version
	clientVersion	the current client version
web3.eth.Eth		Exposes the following properties and methods to interact with the RPC APIs under the eth_ namespace.
eth_account.account.Account		The primary entry point for working with Ethereum private keys.
eth_keys.KeyAPI		the primary API for interacting with the eth-keys libary.
eth_keys.KeyAPI.Signatrue

Basic Usage

Using Brownie and Web3.py together.

>>> web3.eth.coinbase
'0xb009cd53957c0D991CAbE184e884258a1D7b77D9'
>>> web3.eth.getBalance(web3.eth.coinbase)
9995080120300000000000
>>> for acc in web3.eth.accounts[:10]: print(f'{acc}, {web3.eth.getBalance(acc):,}')
...
0xb009cd53957c0D991CAbE184e884258a1D7b77D9, 9,995,080,120,300,000,000,000
0x05f9301Be8F3C133fC474F8d538fD732CaCa274c, 10,000,000,000,000,000,000,000
0x3DC9b4063a130535913137E40Bed546Ff93b1131, 10,000,000,000,000,000,000,000
0x770b1A8d293d152B8Cc9fC01531B1baB3469AF05, 10,000,000,000,000,000,000,000
0xAB3ca295454D4A4de79aE32474d2C82f2D0836b1, 10,000,000,000,000,000,000,000
0x876e0cab3dfC5d2EA19f9A9e6029E8C1b90452Ed, 10,000,000,000,000,000,000,000
0xBb9Bb87EfE2Cf5E024f32c5943311FdA471848Ca, 9,999,898,673,800,000,000,000
0x950ea7798112705f487F657E93Fe5D64557CD138, 9,999,950,898,650,000,000,000
0xA797051B95915F31464440A590332e3360bfEDb9, 9,999,696,040,100,000,000,000
0x9Ebe0ec1f5f2c0f6BA7d9f7187d6f5c540F2b5fa, 10,000,000,000,000,000,000,000
>>> web3.eth.blockNumber
289
>>> web3.eth.getBlock('latest')
AttributeDict({'number': 289, 'hash': HexBytes('0x6e432624d1d6730962cab95e48bf67be818a589f038851d63af3b8c748992633'), 'parentHash': HexBytes('0x8187ad82fc911ffe4658e491dc561ff1526690f4380ea6ff4250b80b865f363e'), 'mixHash': HexBytes('0x0000000000000000000000000000000000000000000000000000000000000000'), 'nonce': HexBytes('0x0000000000000000'), 'sha3Uncles': HexBytes('0x1dcc4de8dec75d7aab85b567b6ccd41ad312451b948a7413f0a142fd40d49347'), 'logsBloom': HexBytes('0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000'), 'transactionsRoot': HexBytes('0x2ab22b1c6b26e27b38af339fa2680a78801de67d7caba46b8c7a01f9fdca9ec7'), 'stateRoot': HexBytes('0x395bc4b216dfcd92a25124d3233010e5c130dc3f07cfd75a0a4c7670346a3f62'), 'receiptsRoot': HexBytes('0xc216ea002b476d3fcf65c0e0d5412cb69831da68ded61246d306b6060c57d82f'), 'miner': '0x0000000000000000000000000000000000000000', 'difficulty': 0, 'totalDifficulty': 0, 'extraData': HexBytes('0x'), 'size': 1000, 'gasLimit': 400000000, 'gasUsed': 26697, 'timestamp': 1609224132, 'transactions': [HexBytes('0x4ef99b474888675edb0f3aa28c310eeb506fa00390f06723b58cc960c9b1ff48')], 'uncles': []})
>>> web3.eth.getBlock(0)
AttributeDict({'number': 0, 'hash': HexBytes('0x515ff4d96e5ab4131d4cd9443ba4dd51ba92b1402f2a79416372efa9945b5094'), 'parentHash': HexBytes('0x0000000000000000000000000000000000000000000000000000000000000000'), 'mixHash': HexBytes('0x0000000000000000000000000000000000000000000000000000000000000000'), 'nonce': HexBytes('0x0000000000000000'), 'sha3Uncles': HexBytes('0x1dcc4de8dec75d7aab85b567b6ccd41ad312451b948a7413f0a142fd40d49347'), 'logsBloom': HexBytes('0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000'), 'transactionsRoot': HexBytes('0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421'), 'stateRoot': HexBytes('0xb477958b9dd0e44345b14ca1dc539ee49098710340252b3ba9ecb289a93a4b89'), 'receiptsRoot': HexBytes('0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421'), 'miner': '0x0000000000000000000000000000000000000000', 'difficulty': 0, 'totalDifficulty': 0, 'extraData': HexBytes('0x'), 'size': 1000, 'gasLimit': 400000000, 'gasUsed': 0, 'timestamp': 1609222192, 'transactions': [], 'uncles': []})
>>>

---

OpenZeppelin

• https://openzeppelin.com/
• Desc. : provides tools to write, deploy and operate decentralized applications.
• License : MIT
• Sources : https://github.com/OpenZeppelin
  • Contracts library : https://github.com/OpenZeppelin/openzeppelin-contracts
  • Upgrades library : https://github.com/OpenZeppelin/openzeppelin-upgrades
  • Test Helpers library : https://github.com/OpenZeppelin/openzeppelin-test-helpers
  • Test Environment library : https://github.com/OpenZeppelin/openzeppelin-test-environment

References

Contracts

• v4.x
  • OpenZeppelin Contracts v4.x Guides
  • OpenZeppelin Contracts v4.x API
  • OpenZeppelin Contracts v4.0 sources

• v3.x
  • OpenZeppelin Contracts v3.x Guides
  • OpenZeppelin Contracts v3.x API
  • OpenZeppelin Contracts v3.4 sources

• v2.x
  • OpenZeppelin Contracts v2.x Guides
  • OpenZeppelin Contracts v2.x API
  • OpenZeppelin Contracts v2.5.1 sources

Contract	Source	Description	Remarks
Ownable	Ownable.sol
AccessControl	AccessControlEnumerable.sol	allows children to implement role-based access control mechanisms.
EnumerableSet	EnumerableSet.sol	Library for managing sets of primitive types.	Bytes32Set, AddressSet, UintSet
EnumerableMap	EnumerableMap.sol	Library for managing an enumerable variant of Solidity’s mapping type.	UintToAddressMap]
ERC 20	ERC20 contracts	the most widespread token standard for fungible assets
ERC 721	ERC721 contracts	the de-facto solution for non-fungible tokens
ERC 777	ERC 777 contracts	a richer standard for fungible tokens

• How to implement ERC20 supply mechanisms (Jan '19)

Test Helpers

• Desc. : Assertion library for Ethereum smart contract testing

• OpenZeppelin Test Helpers API
• OpenZeppelin Test Helpers Configuration

API	Description	Remarks
expectEvent
expectEvent.inTransaction
expectEvent.notEmitted

Test Environment

• Desc. : Blazing fast smart contract testing.

• OpenZeppelin Test Environment API

---

MetaMask

• https://metamask.io
• Desc. : A crypto wallet & gateway to blockchain apps
• License :
• Sources : https://github.com/MetaMask

References

• Data Structure

network = name, rpc-url, chain-id, [currency-symbol], [block-explorer-url]

• Connecting

Network	Chain ID	Currency Symbol	RPC URL	Block Explorer
Binance Smart Chain Mainnet	56	BNB	https://bsc-dataseed.binance.org/	https://bscscan.com
Binance Smart Chain Testnet	97	BNB	https://data-seed-prebsc-1-s1.binance.org:8545/	https://testnet.bscscan.com
Klaytn Testnet (Baobab)	1001	KLAY	https://api.baobab.klaytn.net:8651/	https://baobab.scope.klaytn.com/

Readings

• How to Export an Account Private Key
  • Exporting your account could be risky as it displays your private key in clear text.

• Breaking Change: No Accounts Exposed by Default (Aug 8, 2018)
• Connecting MetaMask into Klaytn
• Connecting MetaMask to Binance Smart Chain (Oct 20, 2021)

• NFT tokens in your MetaMask wallet
  • While you can add NFTs as custom tokens in the extension, you will not be able to see them natively in the UI.
  • MetaMask Mobile displays NFTs under Collectibles. ... We pull our NFT data from opensea.io, our 3rd party repository for all NFTs.
  • NFT token 1155 is still in development. Our product team is planning to add it sometime in Quarter 4 2021.

---

LightWallet

• https://github.com/ConsenSys/eth-lightwallet
• Desc. : Lightweight JS Wallet for Node and the browser
• License : MIT
• Written in : JavaScript

---

Remix IDE

• https://github.com/ethereum/remix-project
• Desc. : a browser-based compiler and IDE that enables users to build Ethereum contracts with Solidity language and to debug transactions
• License : MIT License

Readings

• Remix official documentation

• Remix IDE + Ganache-CLI
• Installing node-gyp on Windows

• Mainnet deploying array of addresses as constructor parameter in Remix Solidity smart contract does not work (Oct 31 '18)
  • ["0xca35b7d915458ef540ade6068dfe2f44e8fa733c", "0x14723a09acff6d2a60dcdf7aa4aff308fddc160c", "0x4b0897b0513fdc7c541b6d9d7e929c4e5364d2db"]

---

Truffle

• http://truffleframework.com/
• Desc. : a development environment, testing framework and asset pipeline for Ethereum, aiming to make life as an Ethereum developer easier
• License : MIT
• Sources : https://github.com/trufflesuite/truffle

References

• Truffle official documentation
• Command Reference
• Interacting with your contracts
• Truffle Contract Package
• Deployer API
• Assert.sol
• Chai assert API
• Truffle Tutorials

• Truffle v5.2.0 Release Notes
  • Multiple Solidity versions supports
  • New record-keeping system @truffle/db

• Mocha class constructor source code
• Mocha class API
• Mocha command-line usage

Commands

Command	Description	Options	Remarks
init	Initialize new and empty Ethereum project	--force
compile	Compile contract source files.	--all, --quiet, --network, --compiler, --config
compile --list	Fetching solc version list from solc-bin.	--all	solc-bin
migrate	Run migrations to deploy contracts.	--reset, --f, --to, --dry-run
test	Runs some or all tests within the test/ directory as specified.	--show-events

Readings

• The Complete Ethereum Blockchain development Tutorials (Draft)
• Building with Webpack
• “SyntaxError: Unexpected token import” on truffle test (Jul 14 '17) : require Babel
• Ethereum: Deploy on a Private Blockchain - truffle, geth, and private blockchains (07 Mar 2017)
• truffle compile error on windows (29 Jun 2017) : truffle.cmd compile
• USING INFURA (OR A CUSTOM PROVIDER)
• Simple Truffle tests timeout “before all” hook: prepare suite (Aug 12 '19)
• Cannot destructure property `body` of 'undefined' or 'null' (5.1.10 to any later version)
• Asserting reverts when testing Solidity smart contracts with Truffle (13 OCT, 2018)
  • truffle-assertions : adds additional assertions that can be used to test Ethereum smart contracts inside Truffle tests.
  • await truffleAssert.reverts(token.mint(user1, amt, {from: user2}), truffleAssert.ErrorType.REVERT)
• Add subscription support for @truffle/hdwallet-provider #2567 (7 Nov 2019)
  • Monkey patch to support web3.eth.subscribe() function for HDWalletProvider with Web3WsProvider

Test

• How to use bignumbers in truffle tests? (Feb 14 '19)
  • Avoid using toNumber() on any value returned from a contract function
  • Keep the returned value in its original type (BigNumber on Truffle 4.x / web3 0.x, and BN on Truffle 5.x / web3 1.x)
  • For printout, you're best off using toFixed() (or toLocaleString() maybe)

Examples

• example-truffle-library : Example project showing how to use Truffle to create javascript libraries
• truffle-webpack-demo : A demo Webpack + React App using truffle-solidity-loader
• truffle-typescript-example : Minimal example integration of Truffle + TypeScript + TestRPC run in docker, for writing smart contracts on Ethereum blockchain.
• Truffle Box : A set of boilerplates to help developers quickly build distributed applications on the Ethereum blockchain with Truffle.

Tips and Tricks

Typical Truffle Configuration

// https://github.com/trufflesuite/truffle/tree/v5.1.5/packages/hdwallet-provider
// https://web3js.readthedocs.io/en/v1.3.0/web3.html#providers
// https://infura.io/docs/ethereum#section/Choose-a-Network
// https://iancoleman.io/bip39/
const HDWalletProvider = require("@truffle/hdwallet-provider");
const Web3HttpProvider = require('web3-providers-http');
const Web3WsProvider = require('web3-providers-ws');

// https://www.npmjs.com/package/web3-providers-http
const httpOptions = {
  keepAlive: true, timeout: 70000
}

// https://www.npmjs.com/package/web3-providers-ws
const wsOptions = {
  timeout: 600000,

  clientConfig: {
    maxReceivedFrameSize: 100000000,
    maxReceivedMessageSize: 100000000,

    keepalive: true,
    keepaliveInterval: 60000,
  },

  reconnect: { auto: true, delay: 5000, maxAttempts: 5, onTimeout: false }
}


// http://truffleframework.com/docs/advanced/configuration
// https://infura.io/docs/gettingStarted/chooseaNetwork
// https://ethereum.stackexchange.com/questions/27048/comparison-of-the-different-testnets
module.exports = {
  
  contracts_build_directory: "./build/truffle",  // default: ./build/contracts

  networks: {
    
    // https://www.trufflesuite.com/docs/truffle/reference/choosing-an-ethereum-client#truffle-develop
    builtin: {    // truffle built-in client : aka `truffle develop`
      host: '127.0.0.1',
      port: 9545,
      network_id: "*"
    },

    development: {  // local Ganache or Ganache CLI
      host: '127.0.0.1',
      port: 8545,
      network_id: '31',
      gas: 3E8,
      gasPrice: 0,
      websockets: true
    },

    mainnet: {
      provider: () => new HDWalletProvider(
        process.env.BIP39_MNEMONIC, 
        "https://mainnet.infura.io/v3/" + process.env.INFURA_PROJECT_ID),
      network_id: '1'      
    },

    //Ropsten : PoW
    //GitHub : https://github.com/ethereum/ropsten/
    //Explorer : https://ropsten.etherscan.io/
    //Faucet : https://faucet.ropsten.be/
    ropsten: {
      provider: () => new HDWalletProvider(
        process.env.BIP39_MNEMONIC, 
        "https://ropsten.infura.io/v3/" + process.env.INFURA_PROJECT_ID),
      network_id: '3',
      gas: 7E6,
      gasPrice: 1E10
    },

    //Rinkeby : PoA
    //Explorer : https://rinkeby.etherscan.io/
    //Faucet : https://faucet.rinkeby.io/
    //Avg. Block Time : 15s
    rinkeby: {
      provider: () => new HDWalletProvider({
        mnemonic: process.env.BIP39_MNEMONIC, 
        providerOrUrl: new Web3HttpProvider("https://rinkeby.infura.io/v3/" + process.env.INFURA_PROJECT_ID, httpOptions),
        pollingInterval: 10000
      }),
      network_id: '4',
    },
    
    rinkeby_ws: {
      provider: () => {
        // Monkey patch to support `web3.eth.subscribe()` function
        // https://github.com/trufflesuite/truffle/issues/2567
        const wsProvider = new Web3WsProvider("wss://rinkeby.infura.io/ws/v3/" + process.env.INFURA_PROJECT_ID, wsOptions);
        HDWalletProvider.prototype.on = wsProvider.on.bind(wsProvider);
        return new HDWalletProvider({
          mnemonic: process.env.BIP39_MNEMONIC,
          providerOrUrl: wsProvider,
          pollingInterval: 10000
        });
      },
      network_id: '4', //https://github.com/ethereum/wiki/wiki/JSON-RPC#net_version
      websockets: true, 
    },

    //Kovan : PoA
    //GitHub : https://github.com/kovan-testnet/
    //Explorer : https://kovan.etherscan.io/
    //Faucet : https://github.com/kovan-testnet/faucet
    //Avg. Block Time : 4s
    kovan: {
      provider: () => new HDWalletProvider({
        mnemonic: process.env.BIP39_MNEMONIC,
        providerOrUrl: new Web3HttpProvider("https://kovan.infura.io/v3/" + process.env.INFURA_PROJECT_ID, httpOptions),
        pollingInterval: 2000
      }),
      network_id: '42', //https://github.com/ethereum/wiki/wiki/JSON-RPC#net_version
      //gas: 7E6,
      //gasPrice: 5E10
    },
    
    kovan_ws: {
      provider: () => {
        // Monkey patch to support `web3.eth.subscribe()` function
        // https://github.com/trufflesuite/truffle/issues/2567
        const wsProvider = new Web3WsProvider("wss://kovan.infura.io/ws/v3/" + process.env.INFURA_PROJECT_ID, wsOptions);
        HDWalletProvider.prototype.on = wsProvider.on.bind(wsProvider);
        return new HDWalletProvider({
          mnemonic: process.env.BIP39_MNEMONIC,
          providerOrUrl: wsProvider,
          pollingInterval: 2000
        });
      },
      network_id: '42', //https://github.com/ethereum/wiki/wiki/JSON-RPC#net_version
      websockets: true, 
      //gas: 7E6,
      //gasPrice: 5E10
    },

    // Goerli : PoA
    // GitHub : https://github.com/goerli/testnet
    // Explorer : https://goerli.etherscan.io/
    // Faucet : 
    // Avg. Block Time : 15s
    goerli: {
      provider: () => new HDWalletProvider({
        mnemonic: process.env.BIP39_MNEMONIC,
        providerOrUrl: new Web3HttpProvider("https://goerli.infura.io/v3/" + process.env.INFURA_PROJECT_ID, httpOptions),
        pollingInterval: 15000
      }),
      network_id: '5'
    },
    
    // Klaytn Testnet
    baobab: {
      provider: () => new HDWalletProvider({
        mnemonic: process.env.BIP39_MNEMONIC,
        providerOrUrl: new Web3HttpProvider("https://api.baobab.klaytn.net:8651/", httpOptions),
        pollingInterval: 2000
      }),
      network_id: '1001'
    },
    
    // Binance Smart Chain Testnet
    // https://docs.binance.org/smart-chain/developer/deploy/truffle.html
    // GitHub : 
    // Explorer : https://testnet.bscscan.com/
    // Faucet : https://testnet.binance.org/faucet-smart
    // Avg. Block Time : 3s
    bsc_test: {
      provider: () => new HDWalletProvider({
        mnemonic: process.env.BIP39_MNEMONIC,
        providerOrUrl: new Web3HttpProvider("https://data-seed-prebsc-1-s1.binance.org:8545", httpOptions),
        pollingInterval: 3500
      }),
      network_id: '97',
      confirmations: 10,
      timeoutBlocks: 200,
      skipDryRun: true
    },    
    
  },

  // https://github.com/mochajs/mocha/blob/v5.2.0/lib/mocha.js#L64
  // https://mochajs.org/#command-line-usage
  mocha: {
    useColors: true,
    enableTimeouts: true,
    timeout: 180000
  },

  // http://truffleframework.com/docs/advanced/configuration
  // https://solidity.readthedocs.io/en/v0.6.6/using-the-compiler.html#target-options
  compilers: {
    solc: {
      version: "pragma",  // https://github.com/trufflesuite/truffle/releases/tag/v5.2.0
      //parser: "solcjs",
      settings: {
        optimizer: {
          enabled: false,
          runs: 200
        },
        evmVersion: "istanbul"  // berlin, istanbul, petersburg, constantinople, byzantium
      }
    },
  },
};

Typical Truffle Test-case

const Token = artifacts.require("TrustedToken");
const Chance = require('chance');
const toBN = web3.utils.toBN;
const { constants, expectEvent, expectRevert } = require('@openzeppelin/test-helpers');

//References
//Truffle test in JavaScript : https://www.trufflesuite.com/docs/truffle/testing/writing-tests-in-javascript
//Truffle Contract Guide : https://www.trufflesuite.com/docs/truffle/getting-started/interacting-with-your-contracts
//Truffle Contract Package : https://github.com/trufflesuite/truffle/tree/master/packages/contract
//Mocha Documentation : https://mochajs.org/#getting-started
//Chai Assert API : https://www.chaijs.com/api/assert/
//Chai Expect/Should API : https://www.chaijs.com/api/bdd/
//OpenZeppelin Test Helpers API : https://docs.openzeppelin.com/test-helpers/0.5/api
//web3 API : https://web3js.readthedocs.io/en/v1.2.11/
//chance.js : https://chancejs.com/
//bn.js : https://github.com/indutny/bn.js/
//JavaScript Reference (MDN) : https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference
//The Modern JavaScript Tutorial : http://javascript.info/

contract("TrustedToken Test Suite 1", async accounts => {
  'use strict';

  // avoid too many accounts
  if(accounts.length > 8) accounts = accounts.slice(0, 8);

  const EventNames = {
    Transfer: 'Transfer',
    Approval: 'Approval'
  };

  async function createFixtures(){
    const chance = new Chance();
    const admin = chance.pickone(accounts);
    const token = await Token.new('Color Token', 'RGB', {from: admin});
    console.debug(`New token contract deployed - address: ${token.address}`);

    return [chance, admin, token];
  }

  before(async() => {
    const table = [];
    let balance = 0;

    // Before test suite, unlock all accounts and display the balances
    for(const acct of accounts){
        await web3.eth.personal.unlockAccount(acct);
        balance = await web3.eth.getBalance(acct);
        await table.push([acct, balance]);
    }

    console.debug(`The number of accounts : ${accounts.length}`);
    console.table(table);
  });

  describe("Minting", () => {
    // mint(), totalSupply(), balanceOf()
    it("Minting tokens should increase the owners balance and total supply", async() =>{
      const [chance, admin, token] = await createFixtures();

      ...
    });

    // mint(), grantRole()
    it("Only minter can 'mint' a token.", async() => {
      const [chance, admin, token] = await createFixtures();

      ...
    });
  });

  describe("Transfer", () => {

    // transfer(), mint()
    it("Transfer should decrease sender's balance and increase recipient's balance as much", async() => {
      const [chance, admin, token] = await createFixtures();
      
      ...
    });

    // mint(), transfer(), totalSupply()
    it("Token transfer should not change total supply.", async() => {
      const [chance, admin, token] = await createFixtures();

      ....
    });

    // transfer(), mint()
    it("Transfer to ZERO address is illegal.", async() => {
      const [chance, admin, token] = await createFixtures();

      ....
    });
    

    ...
  });

  ...
});

---

truffle-assertions

• https://github.com/rkalis/truffle-assertions
• Desc. : adds additional assertions that can be used to test Ethereum smart contracts inside Truffle tests.
• Written-in : JavaScript
• Artifacts : https://www.npmjs.com/package/truffle-assertions

• Asserting reverts when testing Solidity smart contracts with Truffle (13 OCT, 2018)
• Checking events when testing Solidity smart contracts with Truffle (3 MAY, 2018)

---

Hardhat

• https://hardhat.org/
• Desc. : Flexible. Extensible. Fast. Ethereum development environment for professionals
• License :
• Sources : https://github.com/nomiclabs/hardhat

• Hardhat Documentation
• Hardhat Tutorial

---

Embark

• https://github.com/iurimatias/embark-framework
• Desc. : Framework for serverless Decentralized Applications using Ethereum, IPFS and other platforms
• License : MIT

---

Brownie

• https://github.com/eth-brownie/brownie
• Desc. : a Python-based development and testing framework for smart contracts targeting the Ethereum Virtual Machine.
• License : MIT
• Sources :

References

• Brownie Documentation
• Brownie Configuration File (brownie-config.yaml)

Commands

Command	Description	Remarks
brownie init	Initialize a new brownie project
brownie compile	Compile the contract source file
brownie test	Run test cases in the tests/ folder
brownie run	Run a script in the scripts/ folder
brownie console	Load the console
brownie networks	Manage network settings
brownie networks list [verbose=false]	List existing networks

API

• Brownie API

Class	Description	Attributes/Methods	Remarks
ContractContainer	holds all ProjectContract instances of the same type, and is used to deploy new instances of that contract.	abi, signatures, topics, deploy(), at()
Contract	used for interaction with already-deployed contracts that exist outside of a project.
ContractCall	a non state-changing contract method without broadcasting a transaction, and returns the result.
ContractTx	Broadcasts a transaction to a potentially state-changing contract method. Returns a TransactionReceipt.
EventDict	used to hold all events that are fired in a transaction.

Readings

• Getting Started with Brownie: Part 1 (Apr 20, 2020)
• Getting Started with Brownie: Part 2 (Apr 20, 2020)
• Getting Started with Brownie: Part 3 (Apr 20, 2020)

---

ZeppelinOS

• https://zeppelinos.org/
• Desc. : a development platform designed specifically for smart contract projects

---

Mist Browser

• https://github.com/ethereum/mist
• Desc. : the tool of choice to browse and use Ðapps

---

Ganache CLI

• https://github.com/trufflesuite/ganache-cli
• Desc. : simulate full client behavior and make developing Ethereum applications faster, easier, and safer.
• License : MIT

• Ganache-CLI v6.12.1 Options

#! /bin/bash

# TODO
#   - Check the availability of the TCP port for Linux
#   - Setup 'logrotate' for Linux

readonly verbose=1  # 1: true, 0: false - Hard coded yet
readonly dryrun=0   # 1: true, 0: false - Not Used Yet
readonly uname=`uname -s`  # OS type
readonly script_dir=$(cd `dirname $0` && pwd)

declare data_dir
declare log_dir
case $uname in
Linux)  #Linux
  data_dir='/var/lib/ganache-cli'
  log_dir='/var/log'
  ;;
MINGW*)  #Git Bash on Windows
  readonly run_dir=$(mkdir -p "${script_dir}/../run/ganache" && cd "${script_dir}/../run/ganache" && pwd)
  data_dir=${run_dir}/data
  log_dir=${run_dir}
  ;;
Darwin*) #Bash on macOS
  readonly run_dir=$(mkdir -p "${script_dir}/../run/ganache" && cd "${script_dir}/../run/ganache" && pwd)
  data_dir=${run_dir}/data
  log_dir=${run_dir}
  ;;
*)
  echo "The current system is Unknown of which 'uname -s' shows '$uname'."
  exit 600
esac


# check whether GNU getopt is available or not
if [ `getopt --test; echo $?` -ne 4 ]; then
  echo "The avaiable 'getopt' is not GNU getopt which supports long options."
  echo "For MacOS, install 'gnu-getopt' refering 'https://formulae.brew.sh/formula/gnu-getopt'."
  exit 410
fi

options=$(getopt -o rb --long "refresh,background" --name 'ganache-cli-start-options' -- "$@");

if [ $? -ne 0 ]; then
  command=${0##*/}
  echo "Unable to parse command line, which expect '$command [-r|--refresh] [-b|--background]'."
  echo ""
  exit 400
fi

eval set -- "$options"

declare refreshes=0   #false
declare backgrounds=0   #false
while true; do
  case "$1" in
    -r | --refresh )
      echo "refresh specified"
      refreshes=1
      shift ;;
    -b | --background )
      backgrounds=1
      shift ;;
    -- ) shift; break ;;
  esac
done

if [ ! -d "${data_dir}" ]; then
  echo "Creating data directory on '${data_dir}'"
  if [ "$uname" == "Linux" ]; then
    sudo mkdir -p "${data_dir}"
  else
    mkdir -p "${data_dir}"
  fi
fi

if [ $refreshes -eq 1 ]; then
  echo "Removing all current data under '${data_dir}'"
  if [ "$uname" == "Linux" ]; then
    sudo rm -Rf "${data_dir}"
    sleep 3
    sudo mkdir -p "${data_dir}"
  else
    rm -Rf "${data_dir}"
    sleep 3
    mkdir -p "${data_dir}"
  fi
fi

cd "${script_dir}"

readonly eth_ver=`cat ganache-cli.properties | grep -E "^ethereum\.netVersion=" | sed -E 's/ethereum\.netVersion=//'`
readonly eth_host=`cat ganache-cli.properties | grep -E "^ethereum\.host=" | sed -E 's/ethereum\.host=//'`
readonly eth_port=`cat ganache-cli.properties | grep -E "^ethereum\.port=" | sed -E 's/ethereum\.port=//'`
readonly eth_gas_price=`cat ganache-cli.properties | grep -E "^ethereum\.gasPrice=" | sed -E 's/ethereum\.gasPrice=//'`
readonly eth_gas_limit=`cat ganache-cli.properties | grep -E "^ethereum\.gasLimit=" | sed -E 's/ethereum\.gasLimit=//'`
readonly eth_keys=`cat ganache-cli.properties | grep -E "^ethereum\.keys" | sed -E 's/ethereum\.keys\.[0-9]*=//'`

if [ $verbose -ne 0 ]; then
  echo "Ethereum Network ID : $eth_ver"
  echo "Ethereum Client Host Address: $eth_host"
  echo "Ethereum Client TCP Port: $eth_port"
  echo "Ethereum Gas Limit: $eth_gas_limit"
  echo "Ethereum Gas Price: $eth_gas_price"
  echo "Ethereum Private Keys for Accounts: "
  for key in $eth_keys; do echo "    $key"; done
  echo "uname: $uname"
fi

case $uname in
Linux)  #Linux
  echo "Current system is 'Linux'"
  ;;
MINGW*)  #Git Bash on Windows
  echo "Curreun system is 'Windows'"
  # check whether the address is alreasy in use or not
  if [ `netstat -anp tcp | awk '$4 == "LISTENING" {print $2}' | grep -E "^($eth_host|0.0.0.0):$eth_port$" | wc -l` -gt 0 ]; then
    readonly pid=`netstat -anop tcp | awk '$4 == "LISTENING" {print $2 " " $5}' | grep -E "^($eth_host|0.0.0.0):$eth_port\s" | head -n 1 | awk '{print $2}'`
    echo "The address '$eth_host:$eth_port' is already in use by the process of which PID is $pid."
    echo "Fail to start ganache-cli."
    exit 500
  fi
  ;;
Darwin*) #Bash on macOS
  echo "Current system is 'macOS'"
  ;;
*)
  echo "Current system is Unknown of which 'uname -s' shows '$uname'."
  exit 600
esac

# Ganache CLI : https://github.com/trufflesuite/ganache-cli#using-ganache-cli
# BIP 32 : https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki
# BIP 39 : https://github.com/bitcoin/bips/blob/master/bip-0039.mediawiki
#
# Options
#   - gasLimit : The block gas limit (defaults to 0x6691b7)
#   - gasPrice: The price of gas in wei (defaults to 20000000000)

cmd="ganache-cli --networkId $eth_ver \
            --host '$eth_host' \
            --port $eth_port \
            --gasPrice $eth_gas_price \
            --gasLimit $eth_gas_limit"

if [ -n "$eth_keys" ]; then
  echo ""
  echo "Private keys for Ethereum accounts are explicitly specified. They will be used."
  for key in $eth_keys;
    do cmd="${cmd} --account=\"${key},10000000000000000000000\""
  done;
else
  if [ -z "$BIP39_MNEMONIC" ]; then
    echo "'BIP39_MNEMONIC' env. variable is not defined, so implicit default mnemonic will be used."
    echo "If you want to use user defined mnemonic, define it via 'BIP39_MNEMONIC' env. variable and restart this script."
    cmd="${cmd} --deterministic"
  else
    echo "'BIP39_MNEMONIC' env. variable is defined, so it will be used."
    cmd="${cmd} --mnemonic '$BIP39_MNEMONIC'"
  fi
  cmd="${cmd} --defaultBalanceEther 10000 --accounts 10 --secure"
fi

cmd="${cmd} --unlock 0 --unlock 1 --unlock 2 --unlock 3 --unlock 4 \
            --hardfork 'petersburg' \
            --blockTime 0 \
            --db '${data_dir}' >> '${log_dir}'/ganache.log 2>&1"

if [ "$uname" == "Linux" ]; then
  cmd="sudo sh -c \"$cmd\""
  # cmd="sudo sh -c -- $cmd"
fi

if [ $dryrun -ne 0 ]; then
  echo $cmd
  echo ""
  echo "This is 'DRY' run."
  echo "The right above command would be executed, if run again without 'dryrun' option."
  exit 700
fi

if [ $backgrounds -eq 0 ]; then
  echo ""
  echo $cmd
  eval $cmd
else
  cmd=$cmd' &'
  echo ""
  echo $cmd
  eval $cmd

  if [ $? -eq 0 ]; then
    sleep 3
    tail "${log_dir}"/ganache.log -n 50
    echo "The loacal Ganache has started."
    echo "The log file is located at '${log_dir}/ganache.log'."
  fi
fi

---

Oraclize

• http://www.oraclize.it/
• Desc. : the leading oracle service for smart contracts and blockchain applications, serving thousands of requests for day every day on Ethereum, Bitcoin and Rootstock.
• License :

• Readings
  • Oraclzie official documentation

---

BlockScout

• https://github.com/blockscout/blockscout
• Desc. : provides a comprehensive, easy-to-use interface for users to view, confirm, and inspect transactions on EVM (Ethereum Virtual Machine) blockchains.
• License : GPL-3.0 License

• Readings
  • BlockScout documentation

---

Aleth.io

• https://aleth.io/
• Desc. :
• Sources : https://github.com/Alethio

Readings

• Alethio API

---

Memento

• https://github.com/Alethio/memento
• Desc. : a tool to scrape and index data from any web3-compatible networks.
• License : MIT

• Memento documentation

---

Lity

• https://www.litylang.org/
• Desc. : A rule-based contract-oriented high-level language.
• License : GPL-3.0
• Written in : C++
• Sources : https://github.com/second-state/lity

• Components
  • a dynamically extensible language : a superset of the Solidity language
  • a compiler
  • a virtual machine

Readings

• Lity documentation

---

Ethereum plugin for Vault

• https://github.com/immutability-io/vault-ethereum
• Desc. : A plugin that turns Vault into an Ethereum wallet.
• License : Apache-2.0
• Sources : https://github.com/immutability-io/vault-ethereum

Readings

• Using Vault to Build an Ethereum Wallet

---

EthSigner

• https://github.com/PegaSysEng/ethsigner/
• Desc. : A transaction signing application to be used with a web3 provider.
• License : Apache-2.0
• Sources : https://github.com/PegaSysEng/ethsigner/

Readings

• Protecting Your Ethereum Private Key With EthSigner (August 14, 2019)

---

Slither

• https://github.com/crytic/slither
• Desc. : a Solidity static analysis framework
• License : AGPL-3.0

Readings

• Official documentation
• Detector Documentation

Solhint

• https://github.com/protofire/solhint
• Desc. : provides both Security and Style Guide validations.
• License : MIT

Readings

• Official documentation
• List of Rules
• Configuration

---

Mythril

• https://github.com/ConsenSys/mythril
• Desc. : detects security vulnerabilities in smart contracts built for Ethereum, Hedera, Quorum, Vechain, Roostock, Tron and other EVM-compatible blockchains.
• License : MIT

---

Certora

• https://www.certora.com/
• Desc. : Formal verification tool for Solidity
• License : ?

• Compound Smart Contract Spec in Certora Verification Language (CVL)

---

Securify

• https://github.com/eth-sri/securify2
• Desc. : a security scanner for Ethereum smart contracts supported by the Ethereum Foundation and ChainSecurity.
• License :

---

Manticore

• https://github.com/trailofbits/manticore
• Desc. : a symbolic execution tool for analysis of smart contracts and binaries.
• License : AGPL-3.0

---

SmartBugs

• https://github.com/smartbugs/smartbugs
• Desc. : A Framework to Analyze Solidity Smart Contracts
• License : Apache-2.0

---

uPort Identity Contracts

• https://github.com/uport-project/uport-identity
• Desc. :
• License : Apache License

• Different Approaches to Ethereum Identity Standards (Jan 25, 2018)

---

BitGo Ethereum MultiSig Wallet Contract

• https://github.com/BitGo/eth-multisig-v4
• Desc. : Multi-sig contract suitable for use as a 2-of-3 multisig wallet.
• License : Apache-2.0 License

---

Infura

• https://infura.io/
• Desc. : Our suite of high availability APIs and Developer Tools provide quick, reliable access to the Ethereum and IPFS networks so you can focus on building and scaling next generation software.

• Readings
  • Infura Ethereum Documentation
  • Infura Ethereum JSON-PRC Methods

OpenSea

• Developer Tutorials

• Metadata Standards
  • name, description, external_url, background_color, animation_url, youtube_url
• Contract-level metadata

---

Networks

Binance Smart Chain

• https://www.binance.org/en/smartChain
• Desc. : A Parallel Binance Chain to Enable Smart Contracts

• BSC Using Truffle

---

Klaytn

• Klaytn Docs

Network	Description	Block Explorer	Wallet	Faucet
Cypress	Mainnet	https://scope.klaytn.com/	https://wallet.klaytn.com/
Baobab	Testnet	https://baobab.scope.klaytn.com/	https://baobab.wallet.klaytn.com/	https://baobab.wallet.klaytn.com/faucet

Readings

• Connecting to Baobab Public EN

---

Aztec

• https://aztec.network/
• Desc. : an open source layer 2 network bringing scalability and privacy too Ethereum.
• Sources : https://github.com/AztecProtocol

• Aztec Documentation