ECDSASignature.sign constructor

ECDSASignature.sign(ECPrivateKey privkey, Uint8List hash, { bool forceLowR = true, })

Creates a signature using a private key (privkey) for a given 32-byte hash. The signature will be generated deterministically and shall be the same for a given hash and key. If forceLowR is true (default), then signatures with high r-values will be skipped until a signature with a low r-value is found.

Implementation

factory ECDSASignature.sign(
  ECPrivateKey privkey,
  Uint8List hash,
  { bool forceLowR = true, }
) {
  checkBytes(hash, 32);

  Uint8List compact;

  if (forceLowR) {
    // Loop through incrementing entropy until a low r-value is found
    Uint8List extraEntropy = Uint8List(32);
    do {
      compact = secp256k1.ecdsaSign(hash, privkey.data, extraEntropy);
      for (int i = 0; extraEntropy[i]++ == 255; i++) {}
    } while (compact[0] >= 0x80);
  } else {
    compact = secp256k1.ecdsaSign(hash, privkey.data);
  }

  final sig = ECDSASignature.fromCompact(compact);

  // Verify signature to protect against computation errors. Cosmic rays etc.
  if (!sig.verify(privkey.pubkey, hash)) throw InvalidECDSASignature();

  return sig;

}