Design and Primitive Specification for Shannon
Shannon is a synchronous stream cipher with message authentication functionality, designed according to the ECrypt NoE call for stream cipher primitives, profile 1A (but well after the call). Shannon is named in memory of Claude E. Shannon of Bell Labs and MIT, founder of Information Theory. Shannon is an entirely new design, influenced by members of the SOBER family of stream ciphers, Helix/Phelix, Trivium, Scream, and SHA-256. It consists of a single 32-bit wide, 16-element nonlinear feedback shift register and an extra word, which is supplemented for message authentication with 32 parallel CRC-16 registers. Shannon is free to use for any purpose, and reference source code can be found at http://www.qualcomm.com.au/Shannon.html .
An Algebraic Analysis of Trivium Ciphers based on the Boolean Satisfiability Problem
Trivium is a stream cipher candidate of the eStream project. It has successfully moved into phase three of the selection process under the hardware category. No attacks faster than the exhaustive search have so far been reported on Trivium. Bivium-A and Bivium-B are simplified versions of Trivium that are built on the same design principles but with two registers. The simplified design is useful in investigating Trivium type ciphers with a reduced complexity and provides insight into effective attacks which could be extended to Trivium. This paper focuses on an algebraic analysis which uses the boolean satisfiability problem in propositional logic. For reduced variants of the cipher, this analysis recovers the internal state with a minimal amount of keystream observations.