A Large Block Cipher Having a Key on One Side of the Plain Text Matrix and its Inverse on the Other Side as Multiplicants

Abstract

In this paper, we have developed a large block cipher, by modifying the Hill cipher, by multiplying the plain text P with the key K one
side and the modular arithmetic inverse K–1 on the other side. Here, the size of the key is 512 bits and the size of the plain text is 2048bits. From
the cryptanalysis and the avalanche effect studied on this paper, we have seen that the cipher is a very strong one and it cannot be broken by any
cryptanalytic attack.

Keywords: Block cipher, Key, Modular arithmetic inverse, Encryption, Decryption.