Robust encryption is often difficult to achieve on a microcontroller given the limited processing power and memory. The Microchip PIC18 series are capable of some forms of limited data encryption. Four encryption algorithms including AES, XTEA, SKIPJACK® and a simple encryption algorithm using a pseudo-random binary sequence generator are described in this application note.
The power of microcontrollers is limited relative to FPGAs. Nevertheless, Das-labor has developed a set of implementations of different cryptographic algorithms in C designed to function within the limited memory space of microcontrollers. Check out the Avr-Crypto Wiki.
Arnaud Lagger has published some interesting work on the use of FPGAs in encryption. Unlike other docs we’ve seen, this analysis is both comprehensive and detailed, including an appendix with the VHDL source code. Definitely worth the read for anyone interested in encryption using FPGAs.