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Lecture Notes in Computer Science
Irregularly-clocked linear feedback shift registers (LFSRs) are commonly used in stream ciphers. We propose to harness the power of conditional estimators for correlation attacks on these ciphers. Conditional estimators compensate for some of the obfuscating effects of the irregular clocking, resulting in a correlation with a considerably higher bias. On GSM's cipher A5/1, a factor two is gained in the correlation bias compared to previous correlation attacks. We mount an attack on A5/1 usingdoi:10.1007/11693383_1 fatcat:cfy347rfiray3bmulmygejjkga