On decoding techniques for cryptanalysis of certain encryption algorithms

In this paper, important methods for cryptanalysis of the stream cipher bas ed on a class of keystream generators are discussed. These methods employ a ll approach railed the fast correlation attack. This cryptographic problem is treated by considering its equivalent channel coding approach, namely de coding of certain very low rate codes in presence of very high noise. A nov el family of algorithms for tile fast correlation attack is presented. The algorithms are based on the iterative decoding principle in conjunction wit h a novel method for constructing the parity-checks. A goal of this paper i s to summarize reported results and to compare some of the recent ones. Acc ordingly, the family is compared with recently proposed improved fast corre lation attacks based on iterative decoding methods. An analysis of the algo rithms performances: and complexities is presented. The corresponding trade -offs between performance, complexity and required inputs are pointed out.