EVALUATING THE NUMBER OF ACTIVE S-BOXES IN DYNAMIC AES BLOCK CIPHERS USING MDS MATRICES OF SIZE 4×4 AND 8×8

Abstract

AES (Advanced Encryption Standard) was designed by two Belgian cryptographers: Joan Daemen and Vincent Rijmen. AES was recognized as a federal encryption standard by the US National Institute of Standards and Technology on November 26, 2001 and is specified in Federal Information Processing Standard 197 (FIPS 197). However, there have been a number of threats to the security of AES by strong cryptanalysis attacks such as linear, differential cryptanalysis attacks and their variations. Therefore, cryptographic researchers are proposing diverse methods to implement this block cipher dynamically in order to enhance its security. Evaluating the security level of dynamic AES block ciphers is also a significant concern. In this paper, we demonstrate the minimum number of active S-boxes across each four rounds in dynamic AES block ciphers with corresponding and  MDS matrices as  and , respectively. Subsequently, we assess the number of active S-boxes across the rounds of dynamic AES block ciphers using  and  MDS matrices as a basis to demonstrate the security of the dynamic AES block ciphers against linear and differential cryptanalysis across the rounds.