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X25519 in C#

A simple library based on Golang's Curve25519 library.

Features

  • Easy to use front end
  • Completely re written the Golang's crypto library in C#
  • Nearly fast (about 3000 Keys and Agreements/s)
  • Universal library with .Net Standard (You can also use this library anywhere in .Net (Read more below)

Install

Use Nuget

Install-Package Easy-X25519

Link to library on Nuget

Usage

Key Generation

var alice = X25519KeyAgreement.GenerateKeyPair();

In this example, alice is X25519KeyPair struct that contains public key and private key as 32 byte length byte arrays.

Key Agreement

// generate keys
var alice = X25519KeyAgreement.GenerateKeyPair();
var bob = X25519KeyAgreement.GenerateKeyPair();
// generate shared secret
var shared1 = X25519KeyAgreement.Agreement(alice.PrivateKey, bob.PublicKey);
var shared2 = X25519KeyAgreement.Agreement(bob.PrivateKey, alice.PublicKey);
// now the shared1 and shared2 must be same

Use in older versions of .Net

This library is built with .Net Standard 2; Means that minimum frameworks are .Net Core 2 and .Net framework 4.6.1. Full list. You might want to use this library in .Net 2. It's easy to make this library in earlier version of .Net

Note: Due to usage of RNGCryptoServiceProvider this library is not compatible with .Net Core 1.X.

Here are steps to include this library in your project:

  1. At first copy Internal.cs and X25519.cs from here into your project.
  2. If you are using .Net Framework 4 or lower, you will get an error because IReadonlyList is available since .Net framework 4.5. To fix this problem, just change IReadOnlyList<byte> in Internal.cs to byte[]. This should fix the problem.
  3. Use the library

Benchmarks

These benchmarks are done with .Net Core 3.1 on Intel-i7 4790K 4.0GHz.

Full key agreement done in 00:00:00.0093703
Key generation done in 00:00:00.3615465. That is about 2770 keys/sec
Key agreements done in 00:00:00.2800316. That is about 3571 agreement/sec

I also benchmarked the curve25519_generic (not the assembly one) and this library is about twice slower than Golang. Golang key agreement was about 6625 agreement/s.