Obfuscation of logic schemes of pseudo-random number generators based on linear and non-linear feedback shift registers

Abstract

The paper describes methods of protection against reverse engineering of logic circuits of pseudo-random number generators (PRNG) on linear and non-linear feedback shift registers. These methods are based on the use of additional logic elements in the structure of the generator to hide its original functionality. Obfuscation of the generator logic circuit changes its design such that the device works correctly only if the signals at the additional key inputs of the generator take on the correct values. It is shown that even with a small bit capacity of generators, it is possible to provide a huge number of PRNG implementations with different numbers of states and different properties. The concept of a (М + 1)-sequence generator is introduced. The possibility of transforming (M – 1)- and (M – 3)-sequences generators into (M + 1)-sequences generators is demonstrated. The proposed methods can be used to ensure the security of IoT devices.

Keywords

• obfuscation, linear feedback shift register, non-linear feedback shift register, (м + 1)-sequence, pseudo-random number generator.