ChaCha20 in Emacs Lisp

This is a pure Emacs Lisp implementation of the ChaCha20 stream cipher.

This library requires an Emacs built with integers at least 32 bits wide. This typically means a 64-bit build of Emacs. If it passes the test (make check), then you're good to go.

As you would expect, performance is abysmal. It's around 1000x slower than the C reference.

API

(chacha20-create key iv)

Create a new ChaCha20 context initialized with the given 256-bit key and 64-bit nonce. Both key and iv must be unibyte strings.

(chacha20 context)

Generate the next 64 bytes of output in the form of a unibyte string.

(chacha20-unpacked context)

Generate the next 64 bytes of output in the form of 16 32-bit integers. Useful when using ChaCha20 as a PRNG.