Atmel has some of the best and simple RISC architecture microprocessor's out there. Even though they are very simplistic, sometimes you want to do fairly complex things. On one project I was working on I needed an hashing algorithm implemented on the chip. This was my implementation of the SHA1 algorithm for the Atmel AVR product family.

Source code for an SHA1 hashing implementation targeted at the Atmel AVR processor achitectchure. It is written in assembler and currently will only handle input of up to 56 bytes, but extending it to handle more than that is fairly simple. It takes about 127k instructions to perform the algorithm, which on a 8 Mhz chip will take about 15.9 milliseconds. More information about the protocol itself can be found at http://www.itl.nist.gov/fipspubs/fip180-1.htm.