Since Rijndael was chosen as the Advanced Encryption Standard (AES), and became the global encryption standard, improving upon 7-round attacks on the 128-bit key variant or upon 8-round attacks on the 256-bit key variant is considered to be one of the most difficult challenges in the cryptanalysis of block ciphers for more than a decade.

 

We present a novel approach to key-recovery using so-called bicliques.

This allows us to obtain for the first time results on a higher number of

rounds, yet the advantage over brute-force search may become small.

In contrast to most shortcut attack settings on AES versions, we do not

need any related-keys. Our approach is practically verified to a large

extent, yet its full implementation needs prohibitively large computational resources.