The class ElGamalManaged has methods

public override byte[] EncryptData(byte[] p_data);
public override byte[] DecryptData(byte[] p_data);

The task is to add the following methods

public byte[] EncryptData(BigInteger p_data);
public BigInteger DecryptData(byte[] p_data);

as well as the required methods down the line, and cut all the additional work on creating BigIntegers from byte arrays and exporting BigIntegers to byte arrays.

o_random in ElGamalEncryptor is IDisposable and therefore should be disposed. I suggest adding Dispose method to ElGamalEncryptor and making it IDisposable, and do a using (...) {...} in ElGamalManaged.EncryptData (and everywhere else ElGamalEncryptor is used too, if any).

Also, see CA1001 and CA2213

@cheeyixu please fix!

Switch this library to use System.Numerics.BigInteger instead of our own implementation of big integer arithmetics—BigInteger.

It appears as a problem this part of code due to not recognizing ModInverse as a function.

Class: ElGamalDecryptor.cs
Line: A = A.ModInverse(KeyStruct.P);
Issue: ModInverse.

Any idea how to make it work ?

Right now the implementation uses the System.Random random number generator, which is against all rules of cryptography. Needs to be switched over to using System.Security.Cryptography.RNGCryptoServiceProvider.

https://msdn.microsoft.com/en-us/library/system.security.cryptography.rngcryptoserviceprovider(v=vs.110).aspx