Improving AES-128 Using Multiple Cipher Keys and Key Dependent S-Boxes

Abstract

Privacy and Security are the two major advantages that every user strives to achieve in today’s era of digital communication. Sharing and downloading of millions of files by people all over the globe has raised many privacy and security concerns. The sharing of critical data among large corporations, departments and governments is always under the radar of third parties called the adversaries, attackers or hackers. These parties try to exploit the form of communication in order to retrieve the confidential information. This can be avoided using encryption schemes. Encryption schemes are basically of two types- symmetric encryption and asymmetric encryption. AES-128 is one such symmetric encryption scheme, which was standardized in 2001, and is in widespread use for data encryption in today’s world. It uses same key to encrypt and decrypt the data. However, the static nature of keys and Substitution boxes used in the algorithm for AES poses vulnerability for many cryptanalytic attacks. In the proposed work, Chapter 1 aims at discussing the basic concepts in cryptography. Chapter 2 lists the work done by various researchers in order to improve the cryptographic strength of AES-128 and on the basis of observations, objectives are drawn. The detailed discussion on algorithmic implementation of AES-128 is presented in Chapter 3. The proposed methodology, as described in Chapter 4 aims at increasing the cryptographic security by introducing dynamic keys and key-dependent S-Boxes in the conventional AES-128 approach. Chapter 5 presents the results in form of advantages or improvements in quality tested by analyzing the execution time, avalanche effect, and strict avalanche criteria, which tests the randomization of output when input is changed only slightly. Finally, in Chapter 6, the conclusion and future scope has also been mentioned.