I wrote some notes about making mixnet components in Rust that are binary compatible with existing Katzenpost components


The goal should be binary compatibility with the golang implementation of Katzenpost such that the existing golang components can interoperate with the new Rust components. Perhaps the biggest advantage of using Rust would be for writing mixnet clients as opposed to mix servers. A Rust mixnet client could easily present a FFI that could be used by user interfaces written in Java for Android and Swift for iOS.

I wrote several relavant rust crates:

Sphinx binary compatibility

The rust Sphinx uses the exact same cryptographic primitives as the golang implementation. Therefore it should be fairly easy to make them binary compatible. They should share test vectors.

Currently this mix link layer crate uses Noise_XX_25519_ChaChaPoly_BLAKE2b however if the Katzenpost link layer were to upgrade to Kyber then the task of making this crate binary compatibility would be greatly simplified.

Here’s an implementation of Kyber:

This mix_link crate uses the snow Noise protocol library implementation:

However we SHOULD patch snow with Kyber PQ KEM hybrid forward secrecy. Here’s the snow github ticket for this task:

Mix server

Current work in progress rust mix server:

Development progress has halted due to not being able to interoperate with the existing Katzenpost Directory Authority system.