Salsa20 & ChaCha20 Design
Walk through ChaCha20's quarter-round and its speed on mobile hardware.
Welcome
ChaCha20 is the dominant stream cipher in modern systems — used in TLS 1.3, WireGuard, Signal, and many others. Let's dissect its elegant design.
ChaCha20 Origins
Daniel J. Bernstein designed Salsa20 in 2005, then improved it to ChaCha20 in 2008. The 'Cha' prefix indicates 8 additional diffusion improvements. Standardized in RFC 7539 (2015), RFC 8439 (2018).
All lessons in this course
- Stream Cipher Concepts & PRNG
- RC4: Design, Weaknesses & WEP Attacks
- Salsa20 & ChaCha20 Design
- ChaCha20-Poly1305 AEAD in TLS 1.3