Period length optimization linear feedback shift register by adopting bistable multivibrator
Pryo Utomo, Mahyuddin K. M. Nasution, Maya Silvi Lydia · Journal of Physics Conference Series · 2019
Abstract 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. But the random number generated by the algorithm has a repetitive period of numbers. 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. 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. Therefore, this research tries to increase the maximum length of the LFSR algorithm by adopting the bistable multivibrator system steps that applied to electronics. The bistable multivibrator has the ability to change high state to low state and vice versa when it triggered. 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 changes output of the bistable multivibrator will then be used to influence the LFSR algorithm works with XOR gate. 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. Thus the LFSR optimization results with bistable multivibrator have a better impact than the normal LFSR for use in cryptographic systems.