ethers.js/docs.wrm/api/utils/hashing.wrm

_section: Hashing Algorithms @<hashing-algorithms>

There are many hashing algorithms used throughout the blockchain
space as well as some more complex usages which require utilities
to facilitate these common operations.


_subsection: Cryptographic Hash Functions @<cryptographic-hash-functions>

The [Cryptographic Hash Functions](link-wiki-cryptographichash)
are a specific family of hash functions.

_property: ethers.utils.id(text) => string<[[DataHexString]]<32>>  @<utils-id> @SRC<hash>
The Ethereum Identity function computes the [KECCAK256](link-wiki-sha3) hash of the //text// bytes.

_property:  ethers.utils.keccak256(aBytesLike) => string<[[DataHexString]]<32>>  @<utils-keccak256> @SRC<keccak256>
Returns the [KECCAK256](link-wiki-sha3) digest //aBytesLike//.

_property: ethers.utils.ripemd160(aBytesLike) => string<[[DataHexString]]<20>>  @<utils-ripemd160> @SRC<sha2>
Returns the [RIPEMD-160](link-wiki-ripemd) digest of //aBytesLike//.

_property: ethers.utils.sha256(aBytesLike) => string<[[DataHexString]]<32>>  @<utils-sha256> @SRC<sha2:function.sha256>
Returns the [SHA2-256](link-wiki-sha2) digest of //aBytesLike//.

_property: ethers.utils.sha512(aBytesLike) => string<[[DataHexString]]<64>>  @<utils-sha512> @SRC<sha2:function.sha512>
Returns the [SHA2-512](link-wiki-sha2) digest of //aBytesLike//.

_code: KECCAK256 @lang<javascript>

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")
//!

_code: RIPEMD160  @lang<javascript>

utils.ripemd160("0x")
//!

utils.ripemd160("0x1234")
//!

_code: SHA-2  @lang<javascript>

utils.sha256("0x")
//!

utils.sha256("0x1234")
//!

utils.sha512("0x")
//!

utils.sha512("0x1234")
//!


_subsection: HMAC @<utils--hmac>

_property: ethers.utils.computeHmac(algorithm, key, data) => string<[[DataHexString]]>  @<utils-computeHmac> @SRC<sha2>
Returns the [HMAC](link-wiki-hmac) of //data// with //key//
using the [Algorithm](utils--hmac-supported-algorithm) //algorithm//.

_heading: **HMAC Supported Algorithms** @<utils--hmac-supported-algorithm> @SRC<sha2:enum.SupportedAlgorithm>

_property: ethers.utils.SupportedAlgorithm.sha256 => string
Use the [SHA2-256](link-wiki-sha2) hash algorithm.

_property: ethers.utils.SupportedAlgorithm.sha512 => string
Use the [SHA2-512](link-wiki-sha2) hash algorithm.

_code: HMAC  @lang<javascript>

const key = "0x0102"
const data = "0x1234"
utils.computeHmac("sha256", key, data)
//!


_subsection: Hashing Helpers @<utils--hashing-helpers>

_property: ethers.utils.hashMessage(message) => string<[[DataHexString]]<32>>  @<utils-hashMessage> @SRC<hash>
Computes the [[link-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//.

_code: Hashing Messages  @lang<javascript>

// Hashing a string message
utils.hashMessage("Hello World")
//!

// Hashing binary data (also "Hello World", but as bytes)
utils.hashMessage( [ 72, 101, 108, 108, 111, 32, 87, 111, 114, 108, 100 ])
//!

// NOTE: It is important to understand how strings and binary
//       data is handled differently. A string is ALWAYS processed
//       as the bytes of the string, so a hexstring MUST be
//       converted to an ArrayLike object first.

// Hashing a hex string is the same as hashing a STRING
// Note: this is the hash of the 4 characters [ '0', 'x', '4', '2' ]
utils.hashMessage("0x42")
//!

// Hashing the binary data
// Note: this is the hash of the 1 byte [ 0x42 ]
utils.hashMessage([ 0x42 ])
//!

// Hashing the binary data
// Note: similarly, this is the hash of the 1 byte [ 0x42 ]
utils.hashMessage(utils.arrayify("0x42"))
//!


_property: ethers.utils.namehash(name) => string<[[DataHexString]]<32>>  @<utils-namehash> @SRC<hash>
Returns the [ENS Namehash](link-namehash) of //name//.

_code: Namehash  @lang<javascript>

utils.namehash("")
//!

utils.namehash("eth")
//!

utils.namehash("ricmoo.firefly.eth")
//!

utils.namehash("ricmoo.xyz")
//!

_heading: Typed Data Encoder @<TypedDataEncoder> @SRC<hash:class.TypedDataEncoder>

The **TypedDataEncoder** is used to compute the various encoded data required
for [[link-eip-712]] signed data.

Signed data requires a domain, list of structures and their members and the data
itself.

The **domain** is an object with values for any of the standard domain
properties.

The **types** is an object with each property being the name of a structure, mapping
to an array of field descriptions. It should **not** include the ``EIP712Domain``
property unless it is required as a child structure of another.

_note: Experimental Feature (this exported class name will change)
This is still an experimental feature. If using it, please specify the **exact**
version of ethers you are using (e.g. spcify ``"5.0.18"``, **not** ``"^5.0.18"``) as
the exported class name will be renamed from ``_TypedDataEncoder`` to ``TypedDataEncoder`` once
it has been used in the field a bit.

_property: ethers.utils._TypedDataEncoder.from(types) => [TypedDataEncoder] @<TypedDataEncoder-from> @SRC<hash:TypedDataEncoder.from>

Creates a new **TypedDataEncoder** for //types//. This object is a fairly
low-level object that most developers should not require using instances
directly.

Most developers will find the static class methods below the most useful.

_property: TypedDataEncoder.encode(domain, types, values) => string @<TypedDataEncoder-encode> @SRC<hash:staticmethod.TypedDataEncoder.encode>

Encodes the Returns the hashed [[link-eip-712]] domain.

_property: TypedDataEncoder.getPayload(domain, types, value) => any @<TypedDataEncoder-getPayload> @SRC<hash:TypedDataEncoder.getPayload>

Returns the standard payload used by various JSON-RPC ``eth_signTypedData*``
calls.

All domain values and entries in value are normalized and the types are
verified.

_property: TypedDataEncoder.getPrimaryType(types) => string @<TypedDataEncoder-getPrimaryType> @SRC<hash:TypedDataEncoder.getPrimaryType>

Constructs a directed acyclic graph of the types and returns the
root type, which can be used as the **primaryType** for [[link-eip-712]]
payloads.

_property: TypedDataEncoder.hash(domain, types, values) => string<[[DataHexString]]<32>> @<TypedDataEncoder-hash> @SRC<hash:staticmethod.TypedDataEncoder.hash>

Returns the computed [[link-eip-712]] hash.

_property: TypedDataEncoder.hashDomain(domain) => string<[[DataHexString]]<32>> @<TypedDataEncoder-hashDomain> @SRC<hash:TypedDataEncoder.hashDomain>

Returns the hashed [[link-eip-712]] domain.

_property: TypedDataEncoder.resolveNames(domain, types, value, resolveName) => Promise<any> @<TypedDataEncoder-resolveNames> @SRC<hash:TypedDataEncoder.resolveNames>

Returns a copy of value, where any leaf value with a type of ``address`` will have
been recursively replacedwith the value of calling //resolveName// with that value.

_code: Typed Data Example @lang<javascript>

// <hide>
TypedDataEncoder = ethers.utils._TypedDataEncoder
// </hide>

const domain = {
    name: 'Ether Mail',
    version: '1',
    chainId: 1,
    verifyingContract: '0xCcCCccccCCCCcCCCCCCcCcCccCcCCCcCcccccccC'
}

// The named list of all type definitions
const types = {
    Person: [
        { name: 'name', type: 'string' },
        { name: 'wallet', type: 'address' }
    ],
    Mail: [
        { name: 'from', type: 'Person' },
        { name: 'to', type: 'Person' },
        { name: 'contents', type: 'string' }
    ]
}

// The data to sign
const value = {
    from: {
        name: 'Cow',
        wallet: '0xCD2a3d9F938E13CD947Ec05AbC7FE734Df8DD826'
    },
    to: {
        name: 'Bob',
        wallet: '0xbBbBBBBbbBBBbbbBbbBbbbbBBbBbbbbBbBbbBBbB'
    },
    contents: 'Hello, Bob!'
}


TypedDataEncoder.encode(domain, types, value)
//!

TypedDataEncoder.getPayload(domain, types, value)
//!

TypedDataEncoder.getPrimaryType(types)
//!

TypedDataEncoder.hash(domain, types, value)
//!

TypedDataEncoder.hashDomain(domain)
//!


_subsection: Solidity Hashing Algorithms @<utils--solidity-hashing>

When using the Solidity ``abi.packEncoded(...)`` function, a non-standard
//tightly packed// version of encoding is used. These functions implement
the tightly packing algorithm.

_property: ethers.utils.solidityPack(types, values) => string<[[DataHexString]]>  @<utils-solidityPack> @SRC<solidity:pack>
Returns the non-standard encoded //values// packed according to
their respective type in //types//.

_property: ethers.utils.solidityKeccak256(types, values) => string<[[DataHexString]]<32>>  @<utils-solidityKeccak256> @SRC<solidity:keccak256>
Returns the [KECCAK256](link-wiki-sha3) of the non-standard encoded //values// packed
according to their respective type in //types//.

_property: ethers.utils.soliditySha256(types, values) => string<[[DataHexString]]<32>>  @<utils-soliditySha256> @SRC<solidity:sha256>
Returns the [SHA2-256](link-wiki-sha2) of the non-standard encoded //values// packed
according to their respective type in //types//.

_code: Solidity Hashing  @lang<javascript>

utils.solidityPack([ "int16", "uint48" ], [ -1, 12 ])
//!

utils.solidityPack([ "string", "uint8" ], [ "Hello", 3 ])
//!

utils.solidityKeccak256([ "int16", "uint48" ], [ -1, 12 ])
//!

utils.soliditySha256([ "int16", "uint48" ], [ -1, 12 ])
//!

// As a short example of the non-distinguished nature of
// Solidity tight-packing (which is why it is inappropriate
// for many things from a security point of view), consider
// the following examples are all equal, despite representing
// very different values and layouts.

utils.solidityPack([ "string", "string" ], [ "hello", "world01" ])
//!

utils.solidityPack([ "string", "string" ], [ "helloworld", "01" ])
//!

utils.solidityPack([ "string", "string", "uint16" ], [ "hell", "oworld", 0x3031 ])
//!

utils.solidityPack([ "uint96" ], [ "32309054545061485574011236401" ])
//!