Falling into Bytes and Pieces – Cryptanalysis of an Apple Patent Application

In this paper we take a look at a cipher that has escaped public cryptanalysis so far. It is a block cipher published by Apple in a patent application describing its functionality and, as usual for a patent, its innovation. Here, we mainly focus on its security and, as we will see, there are very serious flaws that allow us to break the cipher completely. Moreover, breaking it does not need as much innovation as the patent claims for the cipher itself: Our observations leading to efficient attacks are either generic or tool based.