bazzilic 

A fast and feature-rich BigInteger implementation for .NET. Works faster than the "native" .NET Framework implementation (available in System.Numerics since .NET 4.0) and than the Bouncy Castle implementation. The library is compatible with .NET 2.0+ and is a fully-managed zero-dependency class.

A set of extensions for the .NET BigInteger class

Extension for the .NET Framework cryptography subsystem, which introduces the Paillier public key cryptosystem with support for homomorphic addition.

Extension for the .NET Framework cryptography subsystem, which introduces the ElGamal public key cryptosystem with support for homomorphic multiplication.

Extension for the .NET Framework cryptography subsystem, which introduces the ElGamal public key cryptosystem with support for homomorphic multiplication.

Extension for the .NET Framework cryptography subsystem, which introduces the Paillier public key cryptosystem with support for homomorphic addition.