Salsa20 and ChaCha20
Salsa20 (formerly known as Snuffle 2005) and the closely related ChaCha are stream ciphers developed by Daniel J. Bernstein. Salsa20, the original cipher, was designed in 2005, then later submitted to the eSTREAM European Union cryptographic validation process by Bernstein. ChaCha is a modification of Salsa20 published in 2008. It uses a new round function that increases diffusion and increases performance on some architectures.
Key facts
- Encryption method.name
- ChaCha
- Encryption method.image
- 250px
- Encryption method.caption
- The ChaCha quarter-round function. Four parallel copies make a round.
- Encryption method.designers
- Daniel J. Bernstein
- Encryption method.publish date
- 2008
- Encryption method.derived from
- Salsa20
- Encryption method.derived to
- ChaCha
- Encryption method.related to
- Rumba20
- Encryption method.certification
- eSTREAM portfolio
- Encryption method.key size
- 128 or 256 bits
- Encryption method.state size
- 512 bits
- Encryption method.structure
- ARX
Article
13 sectionsContents
- Structure
- XSalsa20 with 192-bit nonce
- eSTREAM selection of Salsa20
- Cryptanalysis of Salsa20
- ChaCha variant
- XChaCha
- Reduced-round ChaCha
- ChaCha20 adoption
- Internet standards
- See also
- Notes
- References
- External links
Salsa20 (formerly known as Snuffle 2005) and the closely related ChaCha are stream ciphers developed by Daniel J. Bernstein. Salsa20, the original cipher, was designed in 2005, then later submitted to the eSTREAM European Union cryptographic validation process by Bernstein. ChaCha is a modification of Salsa20 published in 2008. It uses a new round function that increases diffusion and increases performance on some architectures.
Both ciphers are built on a pseudorandom function based on add–rotate–XOR (ARX) operations — 32-bit addition, bitwise addition (XOR) and rotation operations. The core function maps a 256-bit key, a 64-bit nonce, and a 64-bit counter to a 512-bit block of the key stream (a Salsa version with a 128-bit key also exists). This gives Salsa20 and ChaCha the unusual advantage that the user can efficiently seek to any position in the key stream in constant time. Salsa20 offers speeds of around 4–14 cycles per byte in software on modern x86 processors, and reasonable hardware performance. It is not patented, and Bernstein has written several public domain implementations optimized for common architectures.