Decrypt Public Key from Keystore File

decrypt-private-key.test.ts

import { decrypt } from 'ethereum-cryptography/aes'
import { keccak256 } from 'ethereum-cryptography/keccak'
import { scrypt } from 'ethereum-cryptography/scrypt'
import { getPublicKey } from 'ethereum-cryptography/secp256k1'
import {
  bytesToHex,
  concatBytes,
  hexToBytes,
  utf8ToBytes,
} from 'ethereum-cryptography/utils'

const keystore = {
  version: 3,
  id: '3529eee7-ac92-4a8c-9b9a-320365541816',
  address: 'f6daa929a5193a877b6ea54fee6c386efda879f2',
  crypto: {
    ciphertext:
      '3d769519fa5a8c92ee4c5ef504edc1fa2e8bcb41134f76c6196f9ed12a2725aa',
    cipherparams: {
      iv: '1f0173c361b2577c018804bd97549c40',
    },
    cipher: 'aes-128-ctr',
    kdf: 'scrypt',
    kdfparams: {
      dklen: 32,
      salt: '61a371af3f72e4bd2b975f0e9c1e10fbecd20bfd58d40da69e8efc2bcf73d56d',
      n: 131072,
      r: 8,
      p: 1,
    },
    mac: '713dc9dabc389bc1bfe3c1de09b9b3df1780020ba870022452e5bccc593a3bdd',
  },
}

const password = 'quantum computer'

it('should decrypt a private key', async () => {
  const { ciphertext, kdfparams, cipherparams, mac } = keystore.crypto

  const derivedKey = await scrypt(
    utf8ToBytes(password),
    hexToBytes(kdfparams.salt),
    kdfparams.n,
    kdfparams.p,
    kdfparams.r,
    kdfparams.dklen
  )

  const messageAuthenticationCode = bytesToHex(
    keccak256(concatBytes(derivedKey.slice(16), hexToBytes(ciphertext)))
  )

  expect(messageAuthenticationCode).toEqual(mac)

  const privateKey = await decrypt(
    hexToBytes(ciphertext),
    derivedKey.slice(0, 16),
    hexToBytes(cipherparams.iv),
    'aes-128-ctr'
  )

  console.log(bytesToHex(privateKey))

  const publicKey = getPublicKey(privateKey)
  const publicKeyWithoutPrefix = publicKey.slice(1) // uncompressed public key has 04 prefix
  const hash = keccak256(publicKeyWithoutPrefix)
  const address = bytesToHex(hash.slice(12))

  expect(address).toEqual(keystore.address)
})