- 1 - Balanced Shrinking Generators

The shrinking generator is a keystream generator which is good for stream ciphers in wireless mobile communications, because it has simple structure and generates a keystream faster than other generators. Nevertheless, it has a serious disadvantage that its keystream is not balanced if they use primitive polynomials as their feedback polynomials. In this paper, we present a method to construct balanced shrinking generators by modifying the structure of the shrinking generator and analyze their cryptographical properties including period, balancedness, linear complexity, and probability distribution. Experimental results show that the keystreams of these generators have larger linear complexity than that of the shrinking generator, provided that the sizes of LFSRs are fixed.