Stream/block cipher crytographic system

Abstract

The system disclosed comprises a dual function cryptographic system capable of operating in either a stream or block cipher mode. Further, with minimal alteration the system is capable of performing either encoding or decoding functions. The system requires three inputs, the first of which is the raw data, and the second two inputs comprise a first and a second unique user supplied key. One of the keys is utilized to control a permutation function for both the stream and block cipher mode and the other key is combined directly with the data in the block cipher mode prior to a series of non-linear transformations. In the stream encipherment mode of operation the second key is entered in its entirety into the system where it is successively and continuously transformed as a function of said first key whereby the function of said system becomes a pseudo-random number generator whose output is serially combined with the raw data to form the stream enciphered cryptogram.