A Fast Correlation Attack for LFSR-Based Stream Ciphers

摘要: This paper describes a novel fast correlation attack of stream ciphers. The salient feature the algorithm is absence any pre-processing or iterative phase, an usual existing attacks. attempts to identify number bits original linear feedback shift register (LFSR) output from received ciphertext. These are then used construct system equations which subsequently solved obtain initial conditions. found perform well for LFSRs large sizes but having sparse polynomials. It may be noted that such polynomials have low Hamming weight one more than connections “taps” corresponding LFSR. Its performance good in situations even where limited cipherlength available. Another important contribution modification approach when LFSR outputs combined by function immune and perhaps, unknown decrypter.