CASTREAM: A new stream cipher suitable for both hardware and software

Abstract

A new Cellular Automata based stream cipher is proposed which is suitable for both hardware and software. It has a non-linear combiner where two non-linear blocks along with a linear block are linearly combined to produce the key-streams. Unlike Non-linear Feedback Shift Register (NFSR) based non-linear combiners, it combines 128-bit blocks using parallel evolution of Cellular Automata (CA) and small CA based S-boxes. The usage of CA prevents the correlation attack and two layers of re-usable small S-boxes prevent the algebraic attacks. The proposed stream cipher takes 128 bits Key and 128 bits of Initial Vector(IV). Theoretically, the cipher operates with an encryption speed of nearly 8 bits per cycle. The initialization process needs 96 cycles which is much faster than Grain and Trivium. This stream cipher is extensible in terms of Key size and provides configurable security and vendor specific implementation option. On implementation, the proposed cipher receives higher throughput than the existing standards. © 2012 Springer-Verlag Berlin Heidelberg.