Base for algebraic cryptanalysis based on combined representation of S-box

摘要

This study reveals an organised algebraic view on the Advanced Encryption Standard (AES), and in particular the S-box. A clear visualisation of algebraic expressions is granted for both the cipher part and the key schedule part of AES. Additionally, by introducing the combined representation of the S-box, alternative methods can be constructed to serve algebraic cryptanalysis on AES. The process to obtain a combined representation of the S-box, as a combination of four bits, the input value's multiplicative inverse and bytes in hexadecimal notion, may be of high importance for other proposed ciphers too built with layers of S-boxes.