Dart

BIP39 Compute Binary Seed from Mnemonic

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Creates a binary seed from a mnemonic. Uses the PBKDF2 function with a mnemonic sentence (in UTF-8 NFKD) used as the password and the string "mnemonic" + passphrase (again in UTF-8 NFKD) used as the salt. The iteration count is set to 2048 and HMAC-SHA512 is used as the pseudo-random function. The length of the derived key is 512 bits (= 64 bytes). Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // This example assumes the Chilkat API to have been previously unlocked.
  // See Global Unlock Sample for sample code.

  final crypt = CkCrypt2();

  // Test with the test vectors at https://github.com/trezor/python-mnemonic/blob/master/vectors.json

  // This is the 2nd test vector..
  final mnemonic = 'legal winner thank year wave sausage worth useful legal winner thank yellow';
  final passphrase = 'TREZOR';
  final expectedSeed = '2e8905819b8723fe2c1d161860e5ee1830318dbf49a83bd451cfb8440c28bd6fa457fe1296106559a3c80937a1c1069be3a3a5bd381ee6260e8d9739fce1f607';
  final expectedMasterKey = 'xprv9s21ZrQH143K2gA81bYFHqU68xz1cX2APaSq5tt6MFSLeXnCKV1RVUJt9FWNTbrrryem4ZckN8k4Ls1H6nwdvDTvnV7zEXs2HgPezuVccsq';

  // The mnemonic sentence (in UTF-8 NFKD) used as the password.
  // The string "mnemonic" + passphrase (again in UTF-8 NFKD) used as the salt.
  // The iteration count is set to 2048 and HMAC-SHA512 is used as the pseudo-random function.
  // The length of the derived key is 512 bits (= 64 bytes). 

  // We want the computed seed to be lowercase hex, therefore our salt must also be hex.
  // The seed is the keyword "mnemonic" + passphrase (in this case is "TREZOR") converted to hex.
  final bdSalt = CkBinData();
  bdSalt.appendString('mnemonic', 'utf-8');
  bdSalt.appendString(passphrase, 'utf-8');

  final computedSeed = crypt.pbkdf2(mnemonic, 'utf-8', 'sha512', bdSalt.getEncoded('hex_lower'), 2048, 512, 'hex_lower');

  print('Expected: $expectedSeed');
  print('Computed: $computedSeed');

  // To compute the hd_master_key, duplicate this Python code:

  //     def to_hd_master_key(seed: bytes, testnet: bool = False) -> str:
  //         if len(seed) != 64:
  //             raise ValueError("Provided seed should have length of 64")
  // 
  //         # Compute HMAC-SHA512 of seed
  //         seed = hmac.new(b"Bitcoin seed", seed, digestmod=hashlib.sha512).digest()
  // 
  //         # Serialization format can be found at: https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki#Serialization_format
  //         xprv = b"\x04\x88\xad\xe4"  # Version for private mainnet
  //         if testnet:
  //             xprv = b"\x04\x35\x83\x94"  # Version for private testnet
  //         xprv += b"\x00" * 9  # Depth, parent fingerprint, and child number
  //         xprv += seed[32:]  # Chain code
  //         xprv += b"\x00" + seed[:32]  # Master key
  // 
  //         # Double hash using SHA256
  //         hashed_xprv = hashlib.sha256(xprv).digest()
  //         hashed_xprv = hashlib.sha256(hashed_xprv).digest()
  // 
  //         # Append 4 bytes of checksum
  //         xprv += hashed_xprv[:4]
  // 
  //         # Return base58
  //         return b58encode(xprv)

  // First compute the HMAC-SHA512 of the computedSeed
  final bdSeed = CkBinData();
  bdSeed.appendEncoded(computedSeed, 'hex_lower');
  crypt.encodingMode = 'hex_lower';
  crypt.hashAlgorithm = 'sha512';
  crypt.setMacKeyString('Bitcoin seed');
  final hmacSha512Hex = crypt.macBdENC(bdSeed);

  final bdHmac = CkBinData();
  bdHmac.appendEncoded(hmacSha512Hex, 'hex_lower');

  final bdXprv = CkBinData();
  bdXprv.appendEncoded('0488ade4', 'hex_lower');
  bdXprv.appendEncoded('000000000000000000', 'hex_lower');
  bdXprv.appendEncoded(bdHmac.getEncodedChunk(32, 32, 'hex_lower'), 'hex_lower');
  bdXprv.appendByte(0);
  bdXprv.appendEncoded(bdHmac.getEncodedChunk(0, 32, 'hex_lower'), 'hex_lower');

  // Double hash using SHA256
  crypt.encodingMode = 'hex_lower';
  crypt.hashAlgorithm = 'sha256';

  final bdHash = CkBinData();
  bdHash.appendEncoded(crypt.hashBdENC(bdXprv), 'hex_lower');
  final secondHash = crypt.hashBdENC(bdHash);
  bdHash.clear();
  bdHash.appendEncoded(secondHash, 'hex_lower');

  // Append the 1st 4 bytes of the bdHash to bdXprv.
  bdXprv.appendEncoded(bdHash.getEncodedChunk(0, 4, 'hex_lower'), 'hex_lower');

  // Base58 encode bdXprv
  final computedMasterKey = bdXprv.getEncoded('base58');

  print('Expected Master Key: $expectedMasterKey');
  print('Computed Master Key: $computedMasterKey');
}