Modified clock-controlled alternating step generators

In this paper, we propose a class of binary keystream generators, called modified clock-controlled alternating step generators, and referred to as ΩKΩK, intended for hardware implementation. This class belongs to the family of clock-controlled generators, and is related to the class of alternating step generators (ASG). Two distinct subclasses of ΩKΩK are investigated in details, namely mixed and linear generators. ΩKΩK has been designed to produce keystreams with guaranteed randomness properties such as long period, high linear complexity and nice statistical distribution properties. The resistance of the proposed generators to well-known cryptanalytic attacks is investigated. Furthermore, the irregular clocking introduced is shown to provide a certain level of strengthened security against several cryptanalytic attacks. Finally, a hardware implementation of a generator of ΩKΩK is provided.