I'm tasked with implementing a DRM on an embedded system. The device would have a limited number of times which it can run, after which it would be disabled, until it syncs with a computer with an internet to be allowed to run again.
For inspiration, I would like to know of embedded device that have similar DRM security and the way they implement it. I have found examples, but would like something on the market.
There's a pretty good description on wikipedia about how FairPlay works, the DRM that iTunes previously used. It's a fairly straightforward combination of public key and symmetric key encryption.
The main addition for embedded systems is the use of code protection schemes built into microcontrollers. Basically, you program a bit that prevents you from reading the code back out. In order to change the code you have to erase it completely first. That prevents someone from just substituting their own encryption keys into the code. Also, if you need unique device keys, those usually have to be programmed individually into EEPROM.
