Never trust a bunny

``Lapin'' is a new RFID authentication protocol proposed at FSE 2012. ``Ring-LPN'' (Ring-Learning-Parity-with-Noise) is a new computational problem proposed in the same paper; there is a proof relating the security of Lapin to the difficulty of Ring-LPN. This paper presents an attack against Ring-LPN-512 and Lapin-512.The attack is not practical but nevertheless violates specific security claims in the FSE 2012 paper