I have put together all the source code, and schematics of Cypher (https://www.youtube.com/watch?v=uZKjCbnfZWw). Cypher is an open source fully portable device aimed for security. The idea of this project was to develop a fully functional personal encryption device for everyday users. Use asymmetric encryption for securing your passwords, files, conversations (such as email through openPGP), and even cryptocurrencies! The use-case example we developed was a personal wallet for cryptocurrencies.
Although this project doesn't uses an AVR, it started with an AVR (one if the earliest prototypes). I just published everything on Hackaday, if anyone's interested, check out the post: https://hackaday.io/project/170403-cypher