Journal:Informatica
Volume 26, Issue 1 (2015), pp. 51–65
Abstract
Abstract
A nonlinear substitution operation of bytes is the main strength factor of the Advanced Encryption Standard (AES) and other modern cipher systems. In this paper we have presented a new simple algorithm to generate key-dependent S-boxes and inverse S-boxes for block cipher systems. The quality of this algorithm was tested by using NIST tests, and changing only one bit of the secret key to generate new key-dependent S-boxes. The fact that the S-boxes are key-dependent and unknown is the main strength of the algorithm, since the linear and differential cryptanalysis require known S-boxes. In the second section of the paper, we analyze S-boxes. In the third section we describe the key-dependent S-boxes and inverse S-boxes generation algorithm. Afterwards, we experimentally investigate the quality of the generated key-dependent S-boxes. Comparison results suggest that the key-dependent S-boxes have good performance and can be applied to AES.
Journal:Informatica
Volume 20, Issue 1 (2009), pp. 23–34
Abstract
Advanced Encryption Standard (AES) block cipher system is widely used in cryptographic applications. A nonlinear substitution operation is the main factor of the AES cipher system strength. The purpose of the proposed approach is to generate the random S-boxes changing for every change of the secret key. The fact that the S-boxes are randomly key-dependent and unknown is the main strength of the new approach, since both linear and differential cryptanalysis require known S-boxes. In the paper, we briefly analyze the AES algorithm, substitution S-boxes, linear and differential cryptanalysis, and describe a randomly key-dependent S-box and inverse S-box generation algorithm. After that, we introduce the independency measure of the S-box elements, and experimentally investigate the quality of the generated S-boxes.