A Modern Hill Cipher Involving a Pair of Keys, Modular Arithmetic Addition and Substitution

In this paper, we have developed a block cipher which involves a pair of keys. Here we have used iteration process which includes functions mix() and substitute() in each round of the iteration process. Function mix() is used for mixing the binary bits of the plaintext, and substitute() is employed for modifying the plaintext. The avalanche effect and the cryptanalysis carried out in this investigation indicate that this cipher cannot be broken by easy means and it is a strong one.