Sosemanuk is a stream cipher developed by Come Berbain, Olivier Billet, Anne Canteaut, Nicolas Courtois, Henri Gilbert, Louis Goubin, Aline Gouget, Louis Granboulan, Cédric Lauradoux, Marine Minier, Thomas Pornin and Hervé Sibert.
Along with HC-128, Rabbit, and Salsa20/12, Sosemanuk is one of the final four Profile 1 (software) ciphers selected for the eSTREAM Portfolio.
The cipher has an improved performance compared with Snow, more specifically by having a faster initialization phase.
The cipher uses an initialization vector of 128 bits.
Of note, during the eSTREAM Phase 1 evaluation process, it was shown that a theoretical attack with cost 2224 could be applied, which does not contradict the security claim of "128 bits".