chacha20

This repository contains an implementation of the chacha20 cipher along with utility functions for using it in practice.

This implementation is tested against the vectors put forward in RFC7539

Usage

This library can be consumed using the add_subdirectory CMake function or by simply copying over the required .c/.h files into your project. /src contains these files.

• chacha.c/h contains an implementation of the chacha block function.
• chacha_stream.c/h contains functions useful for encrypting variable length streams of bytes using chacha.
• chacha_print.c/h provides utility functions for printing and reading in various chacha primitives.

Example

chacha_stream_t stream;
chacha_stream_init(&stream, key, start_block_index, nonce);

chacha_stream_encrypt(&stream, buffer, buffer_length);

See /example directory for full example.

Features to add

• Thorough benchmarking
• More test vectors
• More key and nonce width options
• Poly1305 MAC

Reference documents

• Original paper: https://cr.yp.to/chacha/chacha-20080128.pdf
• Test vectors: https://datatracker.ietf.org/doc/rfc7539/