Abstract

In 1997, the National Institute of Standards and Technology (NIST) announced an open competition for an Advanced Encryption Standard (AES), a symmetric-key cryptographic algorithm, to replace the ageing DES and to be able to run on 128-bit data blocks, using 128-bit, 192-bit or 256-bit keys. After five years of intense peer review, attacks and discussions, the Rijndael algorithm was declared the AES. Being used by the entire world for most of the encryption, it has to be subjected to every possible analysis to find new vulnerabilities. This thesis discusses three new features of the cipher. A powerful attack is initially formulated, which exploits cipher properties in its final and penultimate rounds under applications of precise bit/byte tweaking mechanisms. Next, the Key Schedule of the cipher is simplistically represented and a few interesting properties are noted. Finally, the AES is represented as a set of simple mapping tables and the relevance of such a representation is addressed.