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A Fast Cryptanalysis of the Generalized Self-shrinking Sequences |
Dong Li-hua①②;Zeng Yong②; Hu Yu-pu①② |
①ISN National Key Lab., Xidian University Xi’an 710071 China;②CNIS Key Lab., Ministry of Education China |
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Abstract An initial reconstruction algorithm is given for the generalized self-shrinking sequences using the ideas of the guessing attack. The result shows that: (1) when both the characteristic polynomial of the Linear Feedback Shift Register (LFSR) and the linear combiner are known, the algorithm ensures the cryptanalysis with complexity O((L/2)32L-2)),l≤L/2; (2) when the linear combiner is unknown, the algorithm ensures the cryptanalysis with complexity O(L322L-1),l≤L; (3) When the characteristic polynomial of the LFSR is unknown, the algorithm ensures the cryptanalysis with complexity O(ψ(2L-1)L-122L-l),l≤L. Here L is the length of the LFSR.
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Received: 18 May 2003
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