Keyless entry and ignition are amazingly convenient features to have on your car, but they might just be amazingly convenient for thieves, too.

According to a story in the LeftLane News, technology has advanced to the point where a knowledgeable car thief can crack the encryption on a keyless car security system in about 20 minutes. That's quick enough to drive off with your BMW while you're grabbing a burger, because since the car doesn't require a key to start the ignition, once a thief has the door open, the car is pretty much his.

Although the culprit in the LeftLane story was caught, there's not much real-world advice for avoiding this problem. Computers will only get more powerful, and more cars will adopt keyless technologies. My advice, short of demanding a car with a physically keyed ignition, is this: Consider adding an aftermarket alarm or separate remote control system for handling the car's doors. This way, even if your car uses a keyless ignition, your door locks will be encrypted with a separate technology, doubling the effort required for a car thief. With luck, he'll give up after realizing there are easier targets out there to prey upon.

And of course, there's always The Club.

Do alarms do any good? Got your own car theft horror story, or a trick for deterring thieves? Share them in the comments below!