special base58 encoded holochain agent ids (signing key only)

b58-holochain-keys.js

/*
 * Base58 encoded 32 byte public key
 * includes 7 parity characters (can correct 3 mistyped characters)
 * includes 4 prefix characters (Hkey)
 * is 63 characters long, so can be a dns segment
 *
 * To run this, put it in a directory, and:
 *   npm install base-x
 *   npm install @holochain/n-bch-rs
 *
 * Will output something like:
 *     test buffer: b53a2f27fe96fbbdee9fe23ee11808af1515bc1ae9162d974070a514986eaed3
 *              id: Hkey1DCSFbieX39njvHxm6k98N8bM5kqGx4J5tbKa8SLz5ZGWE3584ECF21DBFE
 *   corrupt start: HZcy1DCSFbieX39njvHxm6k98N8bM5kqGx4J5tbKa8SLz5ZGWE3584ECF21DBFE
 *     corrupt mid: Hkey1DCSFbAAA39njvHxm6k98N8bM5kqGx4J5tbKa8SLz5ZGWE3584ECF21DBFE
 *     corrupt end: Hkey1DCSFbieX39njvHxm6k98N8bM5kqGx4J5tbKa8SLz5ZGWEAAA4ECF21DBFE
 *     corrupt all: Akey1DCSFbAeX39njvHxm6k98N8bM5kqGx4J5tbKa8SLz5ZGWEA584ECF21DBFE
 *     corrupt bad: HkeyAAAAFbieX39njvHxm6k98N8bM5kqGx4J5tbKa8SLz5ZGWE3584ECF21DBFE
 *   all decode success
 */

const ALPHABET = '123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz'

const baseX = require('base-x')
const base58 = baseX(ALPHABET)
const base16 = baseX(ALPHABET.substr(0, 16))
const rs = require('@holochain/n-bch-rs')

const enc = new rs.Encoder(7)
const dec = new rs.Decoder(7)

function baseToBuf (k) {
  const buf = Buffer.alloc(k.length)
  for (let i = 0; i < 52; ++i) {
    buf[i] = ALPHABET.indexOf(k[i])
  }
  return buf
}

function bufToBase (k) {
  const out = []
  for (let i = 0; i < k.byteLength; ++i) {
    if (k[i] < 0 || k[i] >= ALPHABET.length) {
      throw new Error('byte out of base58 range')
    }
    out.push(ALPHABET[k[i]])
  }
  return out.join('')
}

function encode (buffer) {
  let tmp

  tmp = base58.encode(buffer)
  while (tmp.length < 45) {
    tmp = ALPHABET[0] + tmp
  }
  const key = 'Hkey' + tmp

  tmp = baseToBuf(key)
  tmp = enc.encode(tmp)
  tmp = tmp.slice(49)

  const parity = base16.encode(tmp)

  return key + parity
}

function decode (id) {
  let tmp

  tmp = Buffer.concat([
    baseToBuf(id.substr(0, 49)),
    base16.decode(id.substr(49))
  ])

  tmp = dec.correct(tmp)
  tmp = tmp.slice(0, 49)
  tmp = bufToBase(tmp).slice(4)
  tmp = base58.decode(tmp)
  while (tmp.byteLength > 32) {
    tmp = tmp.slice(1)
  }

  return tmp
}

const crypto = require('crypto')

function main () {
  const testBuf = crypto.randomBytes(32)
  console.log('  test buffer:', testBuf.toString('hex'))

  const id = encode(testBuf)
  console.log('           id:', id)

  const res = decode(id).toString('hex')
  if (res !== testBuf.toString('hex')) {
    throw new Error('bad decode: ' + res)
  }

  const test = (tag, id) => {
    console.log(('corrupt ' + tag + ':').padStart(14), id)
    const res = decode(id).toString('hex')
    if (res !== testBuf.toString('hex')) {
      throw new Error('bad decode: ' + res)
    }
  }

  test('start', 'HZc' + id.slice(3))

  test('mid', id.slice(0, 10) + 'AAA' + id.slice(13))

  test('end', id.slice(0, 50) + 'AAA' + id.slice(53))

  test('all',
    'A' + id.slice(1, 10) + 'A' + id.slice(11, 50) + 'A' + id.slice(51))

  ;(() => {
    try {
      const badId = ['H', 'k', 'e', 'y']
      let count = 0
      for (let i of id.slice(4)) {
        if (i === 'A') {
          badId.push('A')
        } else if (count < 4) {
          badId.push('A')
          ++count
        } else {
          badId.push(i)
        }
      }
      test('bad', badId.join(''))
    } catch (e) {
      return
    }
    throw new Error('expected exception, got success')
  })()

  console.log('all decode success')
}

main()