Katholieke Universiteit Leuven
KeeLoq is a lightweight block cipher with a 32-bit block size and a 64-bit key. Despite its short key size, it is used in remote key-less entry systems and other wireless authentication applications. For example, there are indications that authentication protocols based on KeeLoq are used, or were used by various car manufacturers in anti-theft mechanisms. This paper presents a practical key recovery attack against KeeLoq that requires known plaintexts and has a time complexity of KeeLoq encryptions. It is based on the principle of slide attacks and a novel approach to meet-in-the-middle attacks.