The Cryptanalysis of the AES - A Brief Survey.
H. Dobbertin, L. Knudsen, and M. Robshaw.
Abstract:

The Advanced Encryption Standard is more than five years old. Since standardisation there have been few cryptanalytic advances despite the efforts of many researchers. The most promising new approach to AES cryptanalysis remains speculative, while the most effective attack against reduced-round versions is older than the AES itself. Here we summarise this state of affairs.