Self generating multi keys cryptosystem model for noninvertible matrices based on hill cipher Algorithm

Abstract

Many cryptosystems were designed to prevent data from unauthorized access, and some are relatively secure but slow. Others are fast but relatively not secure enough. One of the most efficient cryptosystems is Hill Cipher algorithm which is classified as symmetric encryption. In this paper we provide a solution for the problem of non-invertible matrix by modifying the way of dealing with key matrix, and make all matrices; including not invertible ones, usable in modified Hill cipher system. Moreover, it will solve the known of pair plaintext and cipher text problem by generating new key matrix for each encrypted block of plaintext, using SHA-512. Since SHA- 512 generates 64 integers we can manipulate these integers to become 128 different integers and use them as an input for the matrix; based on the concept that any acceptable data must not be prime.