Read the cryptonomicon! It's a really good intro to a lot of stuff
   that's harder to teach. It's also not too technical, which might help
   you get into things.
   For secure devices you should be worried about:
    * Entropy
    * Radio signals (produced by your electronics)
    * Physical opening of devices (this happens)
    * Lightweight algorithms.
   Sorry to have any specific papers or anything, I think others are
   better capable of recommendations. Have fun out there.