A NOVEL CRYPTOSYSTEM BASED ON FINITE AUTOMATA WITHOUT OUTPUTS

In this paper we introduce a novel cryptosystem based on finite automata without outputs. For encryption and decryption the apparatus uses the same secret keys, which have the transition matrix of a key-automaton without outputs and with an initial state and final states. To each character in the character set of the plaintext there is one or more final states of the key automaton assigned. During encryption the plaintext is read in sequentially character by character and the key automaton assigns to each plaintext character a character string, whose length is adjustable within a given length range. The apparatus creates the ciphertext by linking these character strings together. During decryption the key automaton starting from the initial state reads in the ciphertext character by character and decryption is accomplished by linking together the plaintext characters associated with certain final states, which provides the plaintext in its original form.