bs58check/src/bs58check.js

A straightforward implementation of base58-check encoding

'use strict';

var assert = require('assert')
var base58 = require('bs58')
var crypto = require('crypto')

// SHA256(SHA256(buffer))
function sha256x2(buffer) {
  buffer = crypto.createHash('sha256').update(buffer).digest()
  return crypto.createHash('sha256').update(buffer).digest()
}

// Encode a buffer as a base58-check encoded string
function encode(payload) {
  var checksum = sha256x2(payload).slice(0, 4)

  return base58.encode(Buffer.concat([
    payload,
    checksum
  ]))
}

// Decode a base58-check encoded string to a buffer
function decode(string) {
  var buffer = new Buffer(base58.decode(string))

  var payload = buffer.slice(0, -4)
  var checksum = buffer.slice(-4)
  var newChecksum = sha256x2(payload).slice(0, 4)

  assert.deepEqual(newChecksum, checksum, 'Invalid checksum')

  return payload
}

module.exports = {
  encode: encode,
  decode: decode
}