multikey

Encode and decode in multikey format. Multikey format is a generic, self-describing multicodec-based public key encoding.

Contents

• Install
• Example
• API
  • encode (rawKeyBytes, keyType?)
  • decode (multibaseStr)
  • Module formats
  • pre-built JS

Install

npm i -S @substrate-system/multikey

Example

import { encode, decode } from '@substrate-system/multikey'
const subtle = window.crypto.subtle

// Generate an ed25519 keypair
const keypair = await subtle.generateKey(
    { name: 'Ed25519' },
    true,
    ['sign', 'verify']
)

// Export the public key as raw bytes
const publicKeyBytes = await subtle.exportKey('raw', keypair.publicKey)
const publicKey = new Uint8Array(publicKeyBytes)

// Encode to multikey format (base58btc with 'z' prefix)
// keyType defaults to 'ed25519'
const encoded = encode(publicKey)
console.log(encoded)
// => z6Mk... (a string starting with 'z')

// Decode back to raw key bytes
const decoded = decode(encoded)
console.log(decoded.multicodec)  // => 237 (ed25519-pub)
console.log(decoded.type)        // => 'ed25519'
console.log(decoded.key)         // => Uint8Array(32) [...]

// Round-trip encoding preserves the original key
console.log(decoded.key.toString() === publicKey.toString())  // => true

API

encode (rawKeyBytes, keyType?)

function encode (
    rawKeyBytes:Uint8Array,
    keyType:'ed25519'|'rsa' = 'ed25519'
)

Encode a public key to multikey format.

Parameters:

• rawKeyBytes (Uint8Array) - The raw public key bytes
• keyType ('ed25519' | 'rsa', optional) Default is 'ed25519'

Returns: string - A base58btc-encoded multikey string starting with 'z'

Encode Example

const encoded = encode(publicKey)  // Ed25519 by default
const encodedRsa = encode(rsaPublicKey, 'rsa')  // RSA key

decode (multibaseStr)

function decode (multibaseStr:string):{
    multicodec:number,
    key:Uint8Array<ArrayBufferLike>,
    type:KeyType|'unknown'
}

Decode a multikey format string back to raw key bytes.

Parameters:

• multibaseStr (string) - A multikey string (with or without 'z' prefix)

Returns: { multicodec: number, key: Uint8Array, type: KeyType|'unknown' }

• multicodec - The multicodec identifier (237 for ed25519-pub, 4613 for rsa-pub)
• key - The raw public key bytes
• type - The key type: 'ed25519', 'rsa', or 'unknown'

Decode Example

const decoded = decode('z6Mk...')
console.log(decoded.multicodec)  // 237 or 4613 for ed25519 or rsa
console.log(decoded.type)        // 'ed25519', 'rsa', or 'unknown'
console.log(decoded.key)         // Uint8Array

Module formats

This exposes ESM and common JS via package.json exports field. Works in browsers and Node.

ESM

import { encode, decode } from '@substrate-system/multikey'

Common JS

const multi = require('@substrate-system/multikey')

pre-built JS

This package exposes minified JS files too. Copy them to a location that is accessible to your web server, then link to them in HTML.

copy

cp ./node_modules/@substrate-system/multikey/dist/index.min.js ./public/multikey.min.js

HTML

<script type="module" src="./multikey.min.js"></script>