While acknowledging the success of a theoretical attack, Microchip Technology Inc., Chandler, Ariz., maintains that KeeLoq is still secure.

Researchers claim vehicles can be stolen based on cryptographic findings related to the key’s algorithm. Microchip counters that its system involves much more than the algorithm.

Each remote-control device has a unique key consisting of 18 billion billion values. Even with 100 desktop computers, it would take several decades to discover such a key. Thus Keeloq was thought to be secure.

But researchers at the University of Leuven (Belgium), the Hebrew University, and the Technion in Israel found a way to identify the key using algorithm details that were leaked last year. Their method probes a digital key by wirelessly sending 65,000 challenge/response queries, which takes about an hour. Then, using software they designed, the researchers can decipher the unique code.

Deciphering currently takes about a day using a dedicated computer. But once they’ve cracked one key, they know 36 of the 64 bits they need to know. Those 36 bits are identical for every car model a manufacturer makes (different models vary only slightly). After determining the part of the key common to cars of the same model, the unique bits can be uncovered by eavesdropping during remote locking and unlocking.