Overview

XChaCha-DotNet contains implementations of the following algorithms:

Class	Algorithm	Description
XChaChaAeadCipher	XChaCha20-Poly1305 IETF AEAD	XChaCha AEAD cipher with 192-bit nonce and 192-bit key. Poly-1305 used to compute the authentication tag. Supports Additional Authenticated Data. Can safely encrypt messages up to 2^64 bytes.
XChaChaStream	XChaCha20-Poly1305	XChaCha20 stream cipher using Poly-1305 to compute the authentication tags. Automatically generates and rotates nonces. Supports using Additional Authenticated Data. Can safely encrypt messages up to any practical limit.
XChaChaBufferedStream	XChaCha20-Poly1305	XChaCha20 stream cipher using Poly-1305 to compute the authentication tags. Automatically generates and rotates nonces and buffers the input stream to encrypt data in fixed sized blocks. Can safely encrypt messages up to any practical limit.
XChaChaSecretBoxCipher	XChaCha20-Poly1305	An implementation of the secret_box API in the NaCl crypto library using XChaCha20 for the cipher and Poly-1305 to compute the authentication tag.

Quick Example

Example encryption/decryption using the XChaChaAeadCipher:

Encryption

using (var key = XChaChaKey.Generate())
{
    var aeadCipher = new XChaChaAeadCipher();
    var nonce = XChaChaNonce.Generate();
    var message = Encoding.UTF8.GetBytes("Test Message");
    var ciphertext = aeadCipher.Encrypt(message, key, nonce);
}

Decryption

var keyBytes = Convert.FromBase64String("XPRT6QuYZDdytKM55WW+gnZklhaJBcDnOWi1kEI2we4=");
var nonceBytes = Convert.FromBase64String("2eQuiE8Fy70rwlCAi5T2oVEj5MrwxJaT");
var ciphertext = Convert.FromBase64String("w2jUPkWL0PfvnNFM7xq4o9gcVKrMTkd6SsYhLQ==");
using (var key = new XChaChaKey(keyBytes))
{
    var aeadCipher = new XChaChaAeadCipher();
    var nonce = new XChaChaNonce(nonceBytes);
    var message = aeadCipher.Decrypt(ciphertext, key, nonce);
}