Recently, some mathematical weaknesses of the KeeLoq algorithm have been reported. All of the proposed attacks need at least 2^16 known or chosen plaintexts. In real-world applications of KeeLoq, especially in remote keyless entry systems using a so-called code hopping mechanism, obtaining this amount of plaintext-ciphertext pairs is rather impractical.

We present the first successful DPA attacks on numerous commercially available products employing KeeLoq code hopping. Using our proposed techniques we are able to reveal not only the secret key of remote transmitters in less than one hour, but also the manufacturer key of receivers in less than one day. Knowing the manufacturer key allows for creating an arbitrary number of valid transmitter keys.