Modified AES Cipher Round and Key Schedule

Edjie Malonzo De Los Reyes,Ruji Medina,Ariel M Sison

doi:10.11591/ijeei.v7i1.652

Abstract

In this paper, Advanced Encryption Standard was modified to address the lowdiffusion rate at the early rounds by adding additional primitive operationssuch as exclusive OR and modulo arithmetic in the cipher round. Furthermore,byte substitution and round constant addition were appended to the keyschedule algorithm. The modified AES was tested against the standard AESby means of avalanche effect and frequency test to measure the diffusion andconfusion characteristics respectively. The results of the avalanche effectevaluation show that there was an average increase in diffusion of 61.98% inround 1, 14.79% in round 2 and 13.87% in round 3. Consequently, the resultsof the frequency test demonstrated an improvement in the randomness of theciphertext since the average difference between the number of ones to zeros isreduced from 11.6 to 6.4 along with better-computed p-values. The resultsclearly show that the modified AES has improved diffusion and confusionproperties and the ciphertext can still be successfully decrypted and recoverback the original plaintext.

Highlights

Development of information technology has immensely influenced the change in communication from conventional to digital means [1]-[3], this improvement in communication lead to confidentiality issues especially during the transit of information from source to its intended recipient [4], [5].Information hiding and cryptography are the most common approach in providing information security [6], [7]
The results clearly show that the modified Advanced Encryption Standard (AES) has improved diffusion and confusion properties and the ciphertext can still be successfully decrypted and recover back the original plaintext
The Advanced Encryption Standard (AES) is a symmetric block encryption defined by the Federal Information Processing Standards (FIPS) issued by the National Institute of Standards and Technology (NIST) of the United States of America (USA) and is currently the standard for encryption

Summary

Introduction

Development of information technology has immensely influenced the change in communication from conventional to digital means [1]-[3], this improvement in communication lead to confidentiality issues especially during the transit of information from source to its intended recipient [4], [5]. Information hiding and cryptography are the most common approach in providing information security [6], [7]. Cryptography is used to secure any form of communication system [10]-[12] by scrambling the information so that only the intended recipient can access it. Cryptography uses two general schemes: hashing and encryption. The Advanced Encryption Standard (AES) is a symmetric block encryption defined by the Federal Information Processing Standards (FIPS) issued by the National Institute of Standards and Technology (NIST) of the United States of America (USA) and is currently the standard for encryption

Methods

Results

Conclusion