linear feedback shift register in cryptography

We then shift the register content over by one and add the new output on the end. We take the feedback from the previous outputs and compute a linear combination. That is, we operate on the latest n symbols, saving them to registers.

Note that the last line says to return a linear combination of the previous symbols.

Otherwise return c 1 x 1 + c 2 x 2 + … c n x n mod k.Here’s the algorithm from the previous post: If we set k = 2, the generating algorithm is an example of a linear feedback shift register (LFSR) sequence. As noted near the end of the post, the case k = 2 is especially important in application, i.e. These are optimal sequences that contain every possible consecutive sequence of n symbols from an alphabet of size k. Thus the LFSR optimization results with bistable multivibrator have a better impact than the normal LFSR for use in cryptographic systems.The previous post looked at an algorithm for generating De Bruijn sequences B( k, n) where k is a prime number. Experiments carried out by producing pseudo-random numbers using 30-bit registers 30 times and 4-bit registers 60 times successfully increasing the maximum length with the result twice from the previous maximum period length. The changes output of the bistable multivibrator will then be used to influence the LFSR algorithm works with XOR gate. The adoption process of the bistable multivibrator system is by interpreting high state as a value of '1' and low state as a value of '0'. The bistable multivibrator has the ability to change high state to low state and vice versa when it triggered. Therefore, this research tries to increase the maximum length of the LFSR algorithm by adopting the bistable multivibrator system steps that applied to electronics. It will make a weakness of the cryptographic system because it will make it easier to break the key of the cryptographic system that using pseudo-random generator based the number at the previous period. Repetition of the number will reappear when the LFSR reaches the limit of maximum length and to be new period based on the previous composition of the number that generated.

But the random number generated by the algorithm has a repetitive period of numbers. Linear Feedback Shift Register (LFSR) is one of the algorithms for getting keys in the form the random number that keeps changing unpredictably in cryptographic systems.

Linear feedback shift register in cryptography