Hill Cipher Modifications and Dynamic Cryptosystem Design

Abstract

This paper proposes a highly scalable dynamic cryptosystem, Modified Affine Hill Cipher (AHC-M), which effectively addresses the known vulnerabilities of the classical Hill Cipher and provides an innovative design approach to the development of modern cryptography. By analyzing the existing Hill Cipher variations, the key concepts and design principles, such as non-linear encryption, dynamic key expansion, non-square matrix algebra and dynamic cryptosystem are investigated in detail. Building on these concepts, two practical modifications are proposed that can significantly improve computational complexity and enhance security. We also propose a cryptanalysis technique by extending the chosen-plaintext attack, which can be applied to break the Affine Hill Cipher and serves as a motivation towards the proposed cryptosystem. Lastly, these concepts are generalized as the starting point for further research.