The hackers at Makers Local 256 have created a secure door lock that can use any USB device as a unique key, from a memory stick to a mouse to an iPod. The ingenious system doesn't require you to store anything in memory, which of course could be replicated, because it uses the USB serial number in the chip itself. The authentication process is simple:
• User inserts key into USB hub hooked to a PC
• Computer reads serial ID of key
• Computer compares serial ID to list of valid serial ID in a table \ DB \ Flat File
• If good, computer writes data ("Unlock!") to USB line of Microcontroller
• Microcontroller instructs servo to go to unlocked position for 5-10 seconds.
The project—which uses a Freeduino development board—can be done for about $US60 by anyone with the ability to use a soldering iron. You can find the shopping list, instructions to create the bolt, and code to program the Freeduino. [Makers Local 256 via Hack-a-day]