mnemonicToEntropy function

Uint8List mnemonicToEntropy(List<String> mnemonic)

Implementation

Uint8List mnemonicToEntropy(List<String> mnemonic) {
  if (mnemonic.length % 3 != 0) {
    throw ArgumentError(_invalidMnemonic);
  }
  final wordlist = english;
  // convert word indices to 11 bit binary strings
  final bits = mnemonic.map((word) {
    final index = wordlist.indexOf(word);
    if (index == -1) {
      throw ArgumentError(_invalidMnemonic);
    }
    return index.toRadixString(2).padLeft(11, '0');
  }).join('');
  // split the binary string into ENT/CS
  final dividerIndex = (bits.length / 33).floor() * 32;
  final entropyBits = bits.substring(0, dividerIndex);
  final checksumBits = bits.substring(dividerIndex);

  // calculate the checksum and compare
  final regex = RegExp(r'.{1,8}');
  final entropyBytes = Uint8List.fromList(regex
      .allMatches(entropyBits)
      .map((match) => _binaryToByte(match.group(0)!))
      .toList(growable: false));
  if (entropyBytes.length < 16) {
    throw StateError(_invalidEntropy);
  }
  if (entropyBytes.length > 32) {
    throw StateError(_invalidEntropy);
  }
  if (entropyBytes.length % 4 != 0) {
    throw StateError(_invalidEntropy);
  }
  final newChecksum = _deriveChecksumBits(entropyBytes);
  if (newChecksum != checksumBits) {
    throw StateError(_invalidChecksum);
  }

  return entropyBytes;
}