Improved Multi-Dimensional Meet-in-the-Middle Cryptanalysis of Katan

We study multidimensional meet-in-the-middle attacks on the KATAN block cipher family. Several improvements to the basic attacks are explained. The most noteworthy of these is the technique of guessing only non-linearly involved key bits, which reduces the search space by a significant factor. The optimization decreases the complexity of multidimensional meet-in-the-middle attacks, allowing more rounds of KATAN to be efficiently attacked than previously reported.