Stream cipher is a process of encryption in which where a binary sequence Z, called a Running Key Sequence, is added modulo-2 to the binary plainexts. There are several properties that the sequence (Z) should satisfy in order to secure any cryptanalytic - attack. In this paper the most important properties of (Z) such as period, linear complexity, statistics, correlation immunity and avalanche criterion are discussed.
Systems based on the Multiplexers are then considered and the "Universal Logic System" is modified to give a new and much better running key generator space. Some properties of the new system are proved and empirical results of the other properties are given based on the basis of simulation results.
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