watchdog as random number source

When doing cryptographic functions, unpredictable randomness is needed for things like session keys or sign padding. Here are two implementations, one assembler and one C, that measure the phase noise of the internal freerunning watchdog oscillator and exploits that to genereate a seed buffer.
This seed buffer can then be used to drive a cryptosecure PRNG. In the C example, RC4 is used for this purpose.

PDF with lots of graphs included :-)