/// <summary>
/// Get a Public Key for my Private Key
/// </summary>
/// <param name="secretKey"></param>
/// <returns></returns>
/// <exception cref="ArgumentNullException"></exception>
/// <exception cref="ArgumentException"></exception>
public static byte[] GetPublicKey(byte[] secretKey)
{
if (secretKey == null)
{
throw new ArgumentNullException(nameof(secretKey));
}
if (secretKey.Length != PrivateKeySizeInBytes)
{
throw new ArgumentException($"{nameof(secretKey)} must be {PrivateKeySizeInBytes}");
}
var publicKey = new byte[PrivateKeySizeInBytes];
Array.Copy(sourceArray: secretKey, destinationArray: publicKey, length: PrivateKeySizeInBytes);
ClampOperation.Clamp(s: publicKey);
var a = GroupElementsOperations.ScalarMultiplicationBase(a: publicKey); // To MontgomeryX
var tempX = FieldElementOperations.Add(f: ref a.Z, g: ref a.Y); //Get X
var tempZ = FieldElementOperations.Sub(f: ref a.Z, g: ref a.Y);
tempZ = FieldElementOperations.Invert(z: ref tempZ); //Get Z
// Obtains the Public Key
var publicKeyFieldElement = FieldElementOperations.Multiplication(f: ref tempX, g: ref tempZ); //X*Z
FieldElementOperations.ToBytes(s: publicKey, h: ref publicKeyFieldElement);
return(publicKey);
}
/// <summary>
/// Creates a random private key
/// </summary>
/// <returns>32 random bytes that are clamped to a suitable private key</returns>
public static byte[] GetRandomPrivateKey()
{
var privateKey = new byte[PrivateKeySizeInBytes];
RandomNumberGenerator.Create().GetBytes(privateKey);
ClampOperation.Clamp(s: privateKey, offset: 0);
return(privateKey);
}
