Hybrid FCSR Based Stream Cipher for Secure Communications in IoT

Linear Feedback Shift Register (LFSR) is the basic hardware of stream cipher, and Feedback with Carry Shift Register (FCSR) is the nonlinear analogues of LFSR. FCSR is a feedback architecture to generate long pseudorandom sequence. In this paper, we study the characteristics of FCSRs combined with nonlinear circuits such as Dawson’s Summation Generator (DSG), lp-Geffe generator and etc. Then we proposed a hybrid FCSR applying DSG and lp-Geffe generator as nonlinear combining elements to increase the period and the linear complexity of the output sequence. In addition, we further investigate the period, linear complexity, randomness, and use known attacks to verify the security strength of the proposed keystream generator. The pass rates of the proposed scheme are 100% for FIPS PUB 140-1 random tests, and at least 98% for SP800-22 random test, respectively.