keyless entry systems manufacturerR&D division

Overcoming the Battery Hurdles of Keyless Entry SystemsLimited Battery Capacity Hampers the Fight Against Relay Attacks


Around 10,000 luxury cars are stolen in Japan every year. Relay attacks*, which exploit the vulnerability of keyless entry systems, are on the rise, and both auto manufacturers and makers of keyless entry systems are under pressure to develop defenses against such attacks. The client was one of such manufacturer.

*Relay attack: A theft perpetrated out by a group of thieves who intercept, amplify, and re-transmit (“relay”) the faint radio-frequency signal emitted by a vehicle’s key fob, enabling them to unlock and steal the vehicle, even when it is some distance away from the fob. A problem in Western countries for the last few years, relay attacks are now on the rise in Japan as well.


The Greatest Obstacle Lay in the Power Source

The client’s research and development division was struggling to better understand relay attacks and the issues they present. It was while investigating the possibility of enabling their key fobs to transmit signals that would enable their location to be verified that the team found an issue with the non-rechargeable coin type batteries used as a power supply. The key fobs used in keyless entry systems are powered by non-rechargeable coin type batteries. The R&D team found that due to their low capacities, the non-rechargeable coin type batteries would not support signal transmission. The team therefore decided to try using larger, or additional, batteries to supply the enough power required.

The Team Built a Prototype faced another unexpected issue

While the team first built several prototype key fobs enhanced with relay blocking features, they found that the additional batteries required made the fobs so large that they were no longer portable. No matter how long they worked on the issue, the team came no closer to a breakthrough. They had reached a dead end.

Main Issues

  • Power limitations of the non-rechargeable coin type batteries used in traditional key fobs make it difficult to add additional features.

  • While the team created prototype fobs that could block relay attacks, the additional batteries required made the fobs too large to be carried.