Practical demonstration of the distinguishing attack against the stream cipher NLSv2

The Australian stream cipher NLSv2 [6] is a 32-bit word oriented stream cipher that was quite successful in the stream ciphers competition - the project eSTREAM. The cipher achieved Phase 3 and successfully accomplished one of the main requirements for candidates in Prole 1 (software oriented pro- posals) - to have a better performance than AES in counter mode. However the cipher was not chosen into the nal portfolio [1], because its performance was not so perfect when comparing with other nalist. Also there is a security issue with a high correlation in the used S-Box, which some eective distinguishers exploit. In this paper, a practical demonstration of the distinguishing attack against the smaller version of the cipher is introduced. In our experiments, we have at disposal a machine with four cores (Intel R CoreTM Quad @ 2.66 GHz) and single attack lasts about 6 days. Our results conrmed the assumption and we got 50.0473% zeros in distinguisher.