Fast correlation attacks on certain stream ciphers
Journal of Cryptology
Elements of information theory
Elements of information theory
Linear cryptanalysis method for DES cipher
EUROCRYPT '93 Workshop on the theory and application of cryptographic techniques on Advances in cryptology
Handbook of Applied Cryptography
Handbook of Applied Cryptography
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Feedback polynomials with low degree multiples of low weight should be avoided in linear feedback shift registers when used in nonlinear combiners. We consider another class of weak feedback polynomials, namely the class when taps are located in small groups. This class was introduced in 2004 demonstrating that the resulting distinguishing attack can sometimes be better than the one using low weight multiples. In this paper we take another look at these polynomials and give further insight to the theory behind the attack complexity. Using the Walsh transform we show an easy way to determine the attack complexity given a polynomial. Further, we show that the size of the vectors should sometimes be larger than previously known. We also give a simple relation showing when the new attack will outperform the simple attack based on low weight multiples.