Sosemanuk is a stream cipher

Stream cipher

In cryptography, a stream cipher is a symmetric key cipher where plaintext digits are combined with a pseudorandom cipher digit stream . In a stream cipher the plaintext digits are encrypted one at a time, and the transformation of successive digits varies during the encryption...

 developed by Come Berbain, Olivier Billet, Anne Canteaut, Nicolas Courtois

Nicolas Courtois

Nicolas Tadeusz Courtois is a cryptographer, a senior lecturer in computer science at University College London.Courtois was one of the co-authors of both the XSL attack against block ciphers such as the Advanced Encryption Standard and the XL system for solving systems of algebraic equations, used...

, Henri Gilbert, Louis Goubin, Aline Gouget, Louis Granboulan, Cédric Lauradoux, Marine Minier, Thomas Pornin and Hervé Sibert. Along with HC-128, Rabbit

Rabbit (cipher)

Rabbit is a high-speed stream cipher first presented in February 2003 at the 10th FSE workshop. In May 2005, it was submitted to the eSTREAM project of the ECRYPT network....

, and Salsa20

Salsa20

Salsa20 is a stream cipher submitted to eSTREAM by Daniel Bernstein. It is built on a pseudorandom function based on 32-bit addition, bitwise addition and rotation operations, which maps a 256-bit key, a 64-bit nonce , and a 64-bit stream position to a 512-bit output...

/12, Sosemanuk is one of the final four Profile 1 (software) ciphers selected for the eSTREAM

ESTREAM

eSTREAM is a project to "identify new stream ciphers suitable for widespread adoption", organised by the EU ECRYPT network. It was set up as a result of the failure of all six stream ciphers submitted to the NESSIE project. The call for primitives was first issued in November 2004. The project was...

 Portfolio.

According to the authors, the structure of the cipher is influenced by the stream cipher SNOW

SNOW

SNOW 1.0, SNOW 2.0, and SNOW 3G are word-based synchronous stream ciphers developed by Thomas Johansson and Patrik Ekdahl at Lund University.-History:...

 and the block cipher

Block cipher

In cryptography, a block cipher is a symmetric key cipher operating on fixed-length groups of bits, called blocks, with an unvarying transformation. A block cipher encryption algorithm might take a 128-bit block of plaintext as input, and output a corresponding 128-bit block of ciphertext...

 Serpent

Serpent (cipher)

Serpent is a symmetric key block cipher which was a finalist in the Advanced Encryption Standard contest, where it came second to Rijndael. Serpent was designed by Ross Anderson, Eli Biham, and Lars Knudsen....

. The cipher has an improved performance compared with Snow, more specifically by having a faster initialization phase. The cipher key length can vary between 128 and 256 bits, but the guaranteed security is only 128 bits. The cipher uses an initialization vector of 128 bits. Of note, two [minor?] weaknesses were discovered during the eSTREAM Phase 1 evaluation process.

Sosemanuk is not patented and "free for any use". The name means "snow snake" in the Cree Indian language because it depends both on Snow and Serpent.

External links

• eSTREAM page on Sosemanuk
• "Sosemanuk, a fast software-oriented stream cipher", a paper by the cipher's authors
• The eSTREAM Portfolio announcement
• all eSTREAM announcements