deriveKeyPair function

KeyPair deriveKeyPair(String seed, int index, { String curve = "ed25519", })

Implementation

KeyPair deriveKeyPair(String seed, int index, {String curve = "ed25519"}) {
  if (!(seed is String)) {
    throw "'seed' must be a string";
  }

  if (!(index is int) || index < 0) {
    throw "index' must be a positive number";
  }

  Uint8List pvBuf = derivePrivateKey(seed, index);

  switch (curve) {
    case "ed25519":
      var curveIdBuf = Uint8List.fromList([0]);
      var signingKey = ed25519.SigningKey(seed: pvBuf);
      Uint8List pubBuf = signingKey.publicKey.toUint8List();
      return KeyPair(
          privateKey: concatUint8List([curveIdBuf, pvBuf]),
          publicKey: concatUint8List([curveIdBuf, pubBuf]));

    case "P256":
      var curveIdBuf = Uint8List.fromList([1]);
      final p256 = ECCurve_prime256v1();

      final point = p256.G;

      final bigInt = BigInt.parse(hex.encode(pvBuf), radix: 16);
      var curvePoint = point * bigInt;
      Uint8List pubBuf = curvePoint!.getEncoded(false);
      return KeyPair(
          privateKey: concatUint8List([curveIdBuf, pvBuf]),
          publicKey: concatUint8List([curveIdBuf, pubBuf]));

    case "secp256k1":
      var curveIdBuf = Uint8List.fromList([2]);
      final secp256k1 = ECCurve_secp256k1();

      final point = secp256k1.G;

      final bigInt = BigInt.parse(hex.encode(pvBuf), radix: 16);

      var curvePoint = point * bigInt;
      Uint8List pubBuf = curvePoint!.getEncoded(false);

      return KeyPair(
          privateKey: concatUint8List([curveIdBuf, pvBuf]),
          publicKey: concatUint8List([curveIdBuf, pubBuf]));

    default:
      throw "Curve not supported";
  }
}