Application of linear consistency test in a ciphertext-only attack on irregularly clocked linear feedback shift registers
نویسنده
چکیده
Linear Consistency Test (LCT) is a well-known algebraic method of cryptanalysis of stream ciphers. In this paper, we use LCT in an attack on a noised irregularly clocked linear feedback shift register (LFSR). We show that it is possible to reconstruct the initial states of both the clocked and the clocking LFSR in this scheme by using an essentially algebraic attack method, such as LCT, as a building block in an attack scenario with noise, which is a correlation attack by its nature. An advantage of the attack compared to other attacks against the same scheme is in the fact that it is not necessary to use search in the initial state reconstruction of the clocked LFSR, which significantly improves the efficiency of the attack. It is shown experimentally that the attack is successful for moderate levels of noise in the system.
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