Areas of Application for Nonlinear Shift Registers in PRS Generators

One of the common basic elements of a modern streaming encryption generator is feedback shift registers. In practice, linear bias shift registers (LFSR) are most commonly used. Such cryptographic primitives have been well proven in use for many years. The main advantages of LFSR are: high speed cryptographic algorithms; application of only the simplest operations of addition and multiplication, hardware implemented in almost all computing devices; good cryptographic properties (generated sequences have a long period and good statistical characteristics); are well suited for systems with low energy consumption; ease of analysis using algebraic methods due to linear structure. However, despite the prospects for the use of NLFSR as one of the main elements of the PRS generator, many fundamental problems associated with NLFSR remain insufficiently studied. To date, even such a simple characteristic as the sequence period formed by shift registers, in the feedback of which nonlinearity is introduced, is difficult to determine. In view of the above, the design of cryptographically stable PRS generation systems based on shift registers, which are resistant to various types of attacks and have good technical characteristics, is currently an urgent and necessary task.