Variable-length Hill Cipher with MDS Key Matrix

TL;DR

This paper proposes a strengthened Hill cipher that uses variable-length key matrices derived from an MDS master matrix to improve security against known-plaintext attacks.

Contribution

It introduces a novel method of encrypting plaintext with variable-length MDS-derived key matrices, enhancing the classical Hill cipher's security.

Findings

Increased resistance to known-plaintext cryptanalysis.

Effective use of MDS matrices for key diversification.

Enhanced security without significant performance loss.

Abstract

The Hill Cipher is a classical symmetric cipher which breaks plaintext into blocks of size m and then multiplies each block by an m by m key matrix to yield ciphertext. However, it is well known that the Hill cipher succumbs to cryptanalysis relatively easily. As a result, there have been efforts to strengthen the cipher through the use of various techniques e.g. permuting rows and columns of the key matrix to encrypt each plaintext vector with a new key matrix. In this paper, we strengthen the security of the Hill cipher against a known-plaintext attack by encrypting each plaintext matrix by a variable-length key matrix obtained from a Maximum Distance Separable (MDS) master key matrix.