Exhaustive Key Search of the DES: Updates and Refinements

Exhaustive key search is the simplest attack against a cryptosystem, but it is sometimes the most realistic. This is specially true for carefully designed block ciphers for which advanced cryptanalysis (e.g. : linear, differential) is not applicable. In this paper, we dirst update the cost of an exhaustive key search of the Data Encryption Standard (DES) using Field Programmable Gate Arrays (FPGAs). Then we illus- trate how a time-memory tradeoff attack can be mounted for a similar cost, with much more dramatic consequences.