mnemonicToEntropy static method

Implementation

static String mnemonicToEntropy(String mnemonic) {
  var words = mnemonic.split(' ');
  if (words.length % 3 != 0) throw ArgumentError(_INVALID_MNEMONIC);

  final wordlist = ENGLISH_WORDS;
  // convert word indices to 11 bit binary strings
  final bits = words.map((word) {
    final index = wordlist.indexOf(word);
    if (index == -1) throw ArgumentError(_INVALID_MNEMONIC);

    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(_INVALID_ENTROPY);
  if (entropyBytes.length > 32) throw StateError(_INVALID_ENTROPY);
  if (entropyBytes.length % 4 != 0) throw StateError(_INVALID_ENTROPY);

  final newChecksum = _deriveChecksumBits(entropyBytes);
  if (newChecksum != checksumBits) throw StateError(_INVALID_CHECKSUM);

  return entropyBytes.map((byte) {
    return byte.toRadixString(16).padLeft(2, '0');
  }).join('');
}