Date Added: Dec 2010
This paper introduces an abstract model of reversible sequential machine in designing the cryptosystem based on the symmetric key approach. A reversible sequential machine is a one-to-one mapping old state and input to new state and output. Reversible computing machine is the mapping of old computational state to new computational state is one-to-one. The abstract model of the reversible sequential machine developed here for a cryptosystem is presented as a 4-tuple M(state, input, output, mapping-function) machine. In this machine, the mapping of present state and input to next state and output by residue number system.