True random number generation on an Atmel AVR microcontroller

We present a method of generating true random numbers on an Atmel AVR microcontroller. The jitter of the built-in RC oscillator is used as the source of entropy to generate 8 random bits per second. When implemented on the AVR Butterfly demo board, our method needs no external components; otherwise, only an external oscillator is needed. We tested the generated random bitstream using the “sts” test suite by NIST and discuss the result. Finally, we suggest a possible way of generating slightly more entropy and a method of avoiding external components altogether.