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";
}
final Uint8List pvBuf = derivePrivateKey(seed, index);
switch (curve) {
case 'ed25519':
final Uint8List curveIdBuf = Uint8List.fromList([0]);
final ed25519.SigningKey signingKey = ed25519.SigningKey(seed: pvBuf);
final Uint8List pubBuf = signingKey.publicKey.toUint8List();
return KeyPair(
privateKey: concatUint8List([curveIdBuf, pvBuf]),
publicKey: concatUint8List([curveIdBuf, pubBuf]));
case 'P256':
final Uint8List curveIdBuf = Uint8List.fromList([1]);
final ECCurve_prime256v1 p256 = ECCurve_prime256v1();
final ECPoint point = p256.G;
final BigInt bigInt = BigInt.parse(hex.encode(pvBuf), radix: 16);
final ECPoint? curvePoint = point * bigInt;
final Uint8List pubBuf = curvePoint!.getEncoded(false);
return KeyPair(
privateKey: concatUint8List([curveIdBuf, pvBuf]),
publicKey: concatUint8List([curveIdBuf, pubBuf]));
case 'secp256k1':
final Uint8List curveIdBuf = Uint8List.fromList([2]);
final ECCurve_secp256k1 secp256k1 = ECCurve_secp256k1();
final ECPoint point = secp256k1.G;
final BigInt bigInt = BigInt.parse(hex.encode(pvBuf), radix: 16);
final ECPoint? curvePoint = point * bigInt;
final Uint8List pubBuf = curvePoint!.getEncoded(false);
return KeyPair(
privateKey: concatUint8List([curveIdBuf, pvBuf]),
publicKey: concatUint8List([curveIdBuf, pubBuf]));
default:
throw 'Curve not supported';
}
}