Improved Fast Correlation Attack on the Shrinking and Self-Shrinking generators

In this paper, we propose a fast correlation attack on the shrinking and self-shrinking generator. This attack is an improved algorithm or the fast correlation attack by Zhang et al. at CT-RSA 2005. For the shrinking generator, we recover the initial state of generating LFSR whose length is 61 with keystream bits, the computational complexity of and success probability 99.9%. We also recover the initial state of generating LFSR whose length is of the self-shrinking generator with keystream bits, the computational complexity of and success probability 99.9%.