Modified Alternating k-generators

This paper deals with a class MAGof pseudorandom bit generators - modified alter- nating �-generators. This class is constructed similarly to the class ASGof alternating step genera- tors. Three subclasses of MAGare distinguished, namely linear, mixed and nonlinear generators. The main attention is devoted to the subclass MAG max of linear and mixed generators generating periodic sequences with maximal period lengths. A necessary and sufficient condition for all sequences generated by the linear generators of MAGto be with maximal period lengths is formulated. Such sequences have good statistical properties, such as distribution of zeroes and ones, and large linear complexity. Two methods of cryptanalysis of the proposed generators are given. Finally, three new classes of modified alternating �-generators, designed especially to be more secure, are presented.