We announce the third prize for the most interesting cryptanalysis of Keccak. The results must be publicly available on an URL that is sent to keccak -at- noekeon -dot- org before December 5, 2009 at 23:59 GMT+1 (i.e., before Sinterklaas or Saint Nicolas).

The third prize consists of beer, like the first one. This time we offer Lambic beers that according to myth can only be brewed in the surroundings of Brussels thanks to wild yeast and mysterious bacteria that would not occur anywhere else. Anyway, the prize is a case with 24 (the new number of rounds in Keccak-f) bottles of Lambic-based beers from breweries such as Cantillon, Girardin, and 3 Fonteinen.

Like for the previous prizes, who wins will be decided by consensus in the Keccak team, based internally on a system of points. Some hints:

• Innovative ideas get more points than incremental results or applying standard techniques;
• For attacks with innovations that are comparable, the earlier ones get more points;
• Cryptanalysis or attack techniques applicable to a wider range of valid parameters r, c get more points (see the specifications for the definition of valid parameters);
  • Larger Keccak-f width gets more points;
  • Larger capacity gets more points;
• Attacks on reduced-round versions are allowed but more rounds get more points;
• For the same number of rounds, a distinguisher or attack on the Keccak sponge function gets more points than a distinguisher on Keccak-f only.

We reserve the right to extend the deadline in the absence of interesting results or when we consider that the presented results are too small increments compared to known results.

We hope analyzing Keccak is a fun and interesting challenge, and we appreciate any submitted work!