bb4 is a stream cipher with a 256-bit key, 128-bit nonce, and 512-bit internal states.
bb4 has a similar structure to chacha20. Instead of using 16 32-bit registers, bb4 uses 8 64-bit registers.
Due to the reduced complexity of Permutation and replacement in a single round, bb4 uses 32 rounds.
Consequently, a 512 (or 384) bit PRN is produced after each 32 round.
bb4 is supposed to be the author's toy. It is still in the prototype phase and before cryptanalysis, use it as your own risk.
This repo is implemented in Golang, and we also use chacha20 (without AEAD) as the baseline.
bb4 is designed to:
- Use 64-bit register vectors;
- Be with (or without) AEAD;
- Be fast and vectorized.
Judging from the preliminary results, it passes tests in Dieharder and PractRand.
It is also 29% faster than the chacha20 implementation of the Golang official library (golang.org/x/chacha20).