Hi, I’m trying to figure out a way to lock or unlock parts of source code on the AVR.
What want to achieve is to have only one hex file, but be able to lock or unlock some features (modules) with some kind of a key code, which would be given to the customer.
But I also want to be able to flash the firmware for updates, which the customer can do by himself.
Thus I thought of making some kind of a key or serial number which will be a unique number for each unit.
I thought about using a serial data flash chip, where you can block parts of memory to put a serial number, or even better use the write once only memory bytes that some serial data flash chips have.
Would that be secure enough, which kind of encryption could I use for that?