public static ushort Decrypt(ElGamalKey key, EncryptedMessage encryptedMessage)
{
//apx = a^(p-1-x) mod p
var apx = (ushort)MathUtils.ModularExponentiation(encryptedMessage.A, key.P - 1 - key.X, key.P);
//apx = b*apx mod p
var m = (ushort)((encryptedMessage.B * apx) % key.P);
return(m);
}
public static EncryptedMessage Encrypt(ElGamalKey key, ushort message)
{
Random random = new Random();
var k = random.Next(1, key.P - 1);
// a = g^k mod p
var a = (ushort)MathUtils.ModularExponentiation(key.G, k, key.P);
// b = y^k M mod p
var b = (ushort)MathUtils.ModularExponentiation(key.Y, k, key.P);
var c = (b * message) % key.P;
return(new EncryptedMessage(a, (ushort)c));
}