Key Stream Generator Based on Combination of FCSR and LFSR

A novel stream cipher based on the combination of FCSR and LFSR is proposed by Schneier,which is paid close attention by researchers.In this paper,the properties of this stream cipher are analyzed and the theoretical upper bound of period and that of linear complexity are presented.Then,how to select the parameters of FCSR and LFSR is discussed so that the output sequences can access the theory up bound as much as possible.Meanwhile,the pseudorandom properties of generated sequence are checked by eight tests in NIST STS package.According to the testing results,the generated sequences have good pseudorandom properties if the parameters are selected as the proposed rule.The stream cipher is realized in FPGA and compared with the implementation result of other stream ciphers,which proves this stream cipher is very efficient and can be employed in mobile equipment.