I want to encrypt a few simple text files and exchange them between Delphi on a Windows PC and C in an AVR UC3 embedded processor. Encoding and decoding in both directions.

I was thinking of XTEA or XXTEA or maybe BlowFish, but really, I don't care what the algorithm is; it is much more important to me to just drop in the En/De-code with minimal fuss and have it work in both directions (that means, preferable a single .PAS and a single .C file; preferably standalone and not part of a huge library, with no installation necessary). Files are unlikely to be more than 32kB at any time, probably less.

The files will be on an SD card inside a physically locked (and alarmed) container.

Can anyone recommend some basic s/w with URLs to both Delphi & C?

Thanks in advance