Indefinite block ciphering based on variable and great length key

Abstract

Failure of deterministic encryption algorithms against various attacks mostly occurs due to the use of fixed and deterministic methods for encrypting, decrypting, and key production. Because the key production in these algorithms is performed functionally and deterministically, there is a relation between the keys and their length that makes the differential analysis of the keys possible. Moreover, the fixed length and values of the keys make these algorithms unsafe against exhaustive key searches. In this study, a block cipher algorithm called indefinite block ciphering based on variable and great length key which belongs to probabilistic (nondeterministic) family is presented. In this algorithm, the key depends on the plain text and is produced indecisively by a random number and the connectivity of the different parameters. On the other hand, the plain text is divided into blocks with size of random number. The proposed algorithm was evaluated, and the results were compared with those of the deterministic and other nondeterministic algorithms. This comparison was indicative of the high performance and security of the new algorithm with respect to the other approaches.