Explain what hash functions are?
Cryptographic Hash Functions
The Cryptographic Hash Functions are a specific family of hash functions.
The Ethereum Identity function computs the KECCAK256 hash of the text bytes.
ethers.utils.sha256( aBytesLike ) ⇒ string< DataHexString< 32 > > Returns the SHA2-256 digest of aBytesLike.
ethers.utils.sha512( aBytesLike ) ⇒ string< DataHexString< 64 > > Returns the SHA2-512 digest of aBytesLike.
utils.keccak256([ 0x12, 0x34 ])
//!
utils.keccak256("0x")
//!
utils.keccak256("0x1234")
//!
// The value MUST be data, such as:
// - an Array of numbers
// - a data hex string (e.g. "0x1234")
// - a Uint8Array
// Do NOT use UTF-8 strings that are not a DataHexstring
utils.keccak256("hello world")
//! error
// If needed, convert strings to bytes first:
utils.keccak256(utils.toUtf8Bytes("hello world"))
//!
// Or equivalently use the identity function:
utils.id("hello world")
//!
// Keep in mind that the string "0x1234" represents TWO
// bytes (i.e. [ 0x12, 0x34 ]. If you wish to compute the
// hash of the 6 characters "0x1234", convert it to UTF-8
// bytes first using utils.toUtf8Bytes.
// Consider the following examples:
// Hash of TWO (2) bytes:
utils.keccak256("0x1234")
//!
// Hash of TWO (2) bytes: (same result)
utils.keccak256([ 0x12, 0x34 ])
//!
const bytes = utils.toUtf8Bytes("0x1234");
// <hide>
bytes
// </hide>
//!
// Hash of SIX (6) characters (different than above)
utils.keccak256(bytes)
//!
// Hash of SIX (6) characters (same result)
utils.id("0x1234")
//!
utils.ripemd160("0x")
//!
utils.ripemd160("0x1234")
//!
utils.sha256("0x")
//!
utils.sha256("0x1234")
//!
utils.sha512("0x")
//!
utils.sha512("0x1234")
//!
ethers.utils.computeHmac( algorithm , key , data ) ⇒ string< DataHexString > Returns the HMAC of data with key using the Algorithm algorithm.
HMAC Supported Algorithms
ethers.utils.SupportedAlgorithm.sha256 ⇒ string Use the SHA2-256 hash algorithm.
ethers.utils.SupportedAlgorithm.sha512 ⇒ string Use the SHA2-512 hash algorithm.
const key = "0x0102";
const data = "0x1234";
utils.computeHmac("sha256", key, data)
//!
ethers.utils.hashMessage( message ) ⇒ string< DataHexString< 32 > > Computes the EIP-191 personal message digest of message. Personal messages are converted to UTF-8 bytes and prefixed with \x19Ethereum Signed Message: and the length of message.
// @TODO: include exampels of hashMessage; it can be complex. :)
utils.namehash("")
//!
utils.namehash("eth")
//!
utils.namehash("ricmoo.firefly.eth")
//!
utils.namehash("ricmoo.xyz")
//!
Solidity Hashing Algorithms
When using the Solidity abi.packEncoded(...) function, a non-standard tightly packed version of encoding is used. These functions implement the tightly packing algorithm.
ethers.utils.solidityPack( types , values ) ⇒ string< DataHexString > Returns the non-standard encoded values packed according to their respecive type in types.
ethers.utils.solidityKeccak256( types , values ) ⇒ string< DataHexString< 32 > > Returns the KECCAK256 of the non-standard encoded values packed according to their respective type in types.
ethers.utils.soliditySha256( types , values ) ⇒ string< DataHexString< 32 > > Returns the SHA2-256 of the non-standard encoded values packed according to their respective type in types.
utils.solidityPack([ "int16", "uint48" ], [ -1, 12 ])
//!
utils.solidityPack([ "string", "uint8" ], [ "Hello", 3 ])
//!
utils.solidityKeccak256([ "int16", "uint48" ], [ -1, 12 ])
//!
utils.soliditySha256([ "int16", "uint48" ], [ -1, 12 ])
//!