<PackageReference Include="BouncyCastle.Cryptography" Version="2.3.1" />

Org.BouncyCastle.Crypto.Engines.RsaCoreEngine

public class RsaCoreEngine : IRsa
This does your basic RSA algorithm.
namespace Org.BouncyCastle.Crypto.Engines { public class RsaCoreEngine : IRsa { public virtual void Init(bool forEncryption, ICipherParameters parameters); public virtual int GetInputBlockSize(); public virtual int GetOutputBlockSize(); public virtual BigInteger ConvertInput(byte[] inBuf, int inOff, int inLen); public virtual byte[] ConvertOutput(BigInteger result); public virtual BigInteger ProcessBlock(BigInteger input); public RsaCoreEngine(); } }