The comparing of constructions based on shift registers with a nonlinear feedback of the second order with shift registers with a linear feedback is considered. It is shown that there is a significant advantage in choosing SRNLF generating the sequence with a maximal period in comparing with using SRLF. The expression for determination of the sequence resulting period got by means of summation of a few sequences of different M-SRNLF is received. The recommendations in choosing a dimensionality of forming M-SRNLF to form the summary sequence of a maximal period are given.
stream ciphers, nonlinear systems, period of SRNLF