Augmented Hill Cipher

Abstract

Securing data over an open network is one of the most critical problems in network security. To secure data, an encryption algorithm should be used. Hill cipher is one of most famous encryption algorithms. Although the Hill cipher is not strong enough and vulnerable to many types of attacks, it is still playing a significant role in educational systems; The original Hill cipher is vulnerable to known plaintext attack. In the last decade, Hill cipher got much attention. Researchers proposed many enhances to the Hill cipher; New modifications of the Hill cipher are proposed to enhance the security of Hill cipher. In this paper we shall show that ＂A Modified Hill Cipher Based on Circulant Matrices＂ is vulnerable to both known plaintext attack and chosen plaintext attack. Moreover, we will introduce a new mode of operation which can be used with any block cipher. Then we will propose a new enhanced encryption algorithm. After that, we shall provide a security analysis and efficiency evaluation for our new encryption algorithm.