tweak method
Tweaks the private key with a scalar. In the instance a new key cannot be created (practically impossible for random 32-bit scalars), then null will be returned.
Implementation
ECPrivateKey? tweak(Uint8List scalar) {
checkBytes(scalar, 32, name: "Scalar");
final newScalar = secp256k1.privKeyTweak(_data, scalar);
return newScalar == null ? null : ECPrivateKey(newScalar, compressed: compressed);
}