Implementation of the Most Suitable Mode of Block Cipher Techniques

Abstract

The analysis of performance criteria for different cryptographic algorithms has increasingly been concerned in the last few years and that is because the majority of life applications need cryptographic algorithms to be involved in their structure to provide security for these applications such as banking services, e-government and online applications. In this thesis, the analytic study is executed on the most specific popular cryptographic algorithm which is advanced encryption standard (AES) algorithm in order to study the impact of using different models which are called modes on the behavior of (AES) algorithm and hence increases the cryptographic strength of (AES) algorithm. The criteria used to help in judging on the influence of using different modes on the behavior of (AES) algorithm are encryption time, throughput and strict avalanche criteria (SAC). Such influence has been clarified and presented through providing comparative analysis among the different modes of operation according to previously mentioned criteria using the traditional S-box formula in constructing (AES) algorithm then an enhanced version of S-box called improved S-box is included in (AES) algorithm to provide more complex and securing S-box in constructing (AES) algorithm so as to measure the impact of changing the formula of substitution box on the behavior of (AES) algorithm and its cryptographic capabilities .Finally, the results of executing the modes on the behavior of (AES) algorithm in case of using the traditional s-box and the improved S-box are listed in terms of the previously mentioned criteria encryption time, throughput and (SAC).