seedFromUri method

Future<List<int>> seedFromUri(
  1. String uri, {
  2. String? password,
})

Parses secret uri (URI) into a 32 bytes that can be used to generate a key pair.

The URI is parsed from a string. The string is interpreted in the following way:

  • If string is a possibly 0x prefixed 64-digit hex string, then it will be interpreted directly as a MiniSecretKey (aka "seed" in subkey).
  • If string is a valid BIP-39 key phrase of 12, 15, 18, 21 or 24 words, then the key will be derived from it. In this case:
    • the phrase may be followed by one or more items delimited by / characters.
    • the path may be followed by ///, in which case everything after the /// is treated as a password.
  • If string begins with a / character it is prefixed with the Substrate public DEV_PHRASE and interpreted as above.

In this case they are interpreted as HDKD junctions; purely numeric items are interpreted as integers, non-numeric items as strings. Junctions prefixed with / are interpreted as soft junctions, and with // as hard junctions.

There is no correspondence mapping between SURI strings and the keys they represent. Two different non-identical strings can actually lead to the same secret being derived. Notably, integer junction indices may be legally prefixed with arbitrary number of zeros. Similarly an empty password (ending the SURI with ///) is perfectly valid and will generally be equivalent to no password at all.

Reference: https://github.com/paritytech/substrate/blob/polkadot-v0.9.43/client/cli/src/commands/utils.rs#L57-L154

Implementation

Future<List<int>> seedFromUri(String uri, {String? password}) async {
  try {
    final entropy = Mnemonic.fromSentence(uri, Language.english).entropy;
    final seed = await CryptoScheme.seedFromEntropy(entropy, password: password);
    return seed.sublist(0, 32);
    // ignore: empty_catches
  } catch (e) {}

  final secretUri = SecretUri.fromStr(uri);

  // The phrase is hex encoded secret seed
  if (secretUri.phrase.startsWith('0x')) {
    try {
      return hex.decode(secretUri.phrase.substring(2));
    } catch (e) {
      throw SubstrateBip39Exception.invalidSeed();
    }
  }

  final passwordOverride = password ?? secretUri.password;
  final List<int> entropy;
  try {
    entropy = Mnemonic.fromSentence(secretUri.phrase, Language.english).entropy;
  } on Exception catch (e) {
    throw SubstrateBip39Exception.fromException(e);
  }

  List<int> seed = await CryptoScheme.seedFromEntropy(entropy, password: passwordOverride);
  seed = seed.sublist(0, 32);

  return await derive(seed, secretUri.junctions);
}