Design and Analysis of a new Stream Cipher based on Ring FCSR Automaton

Abstract

Feedback with Carry Shift Registers (FCSRs) are being most commonly used in the design of new stream ciphers. This is because the FCSRs have resistance to correlation and algebraic attacks because of their quadratic feedback [26], [21]. Two representations of FCSRs, namely, Galois and Fibonacci are quite popular. However, stream cipher designed using any of these representations is vulnerable to many attacks as proposed in [16], [15]. A new representation called the ring representation, which generalizes and avoids the weaknesses of both the representations of FCSRs has been proposed in [13]. Similar to other representations, the ring representations produce sequences that have high periods and entropy. The advantage of ring representation is that it results in faster diffusion and reduced implementation costs when compared to Galois and Fibonacci. This paper presents two designs of stream cipher based on ring representations. In both algorithms, the output is produced by linear filters that pass randomness tests. The ciphers proposed have undergone a thorough security analysis.