I'am working on SAMD21 and now I'd like to implement the possibility to encrypted my firmware. I googled but I didn't find any good results, is it possible to do this with an SAMD21? Is anyone have a doc or a tutorial where I can learned how to developped this ?
Have you looked on the Microchip website. This is a link to the web page for "AT02333: Safe and Secure Bootloader Implementation for SAM3/4". The second link (below the app note) is to a zip file that may contain the files you are looking for.