I've been working on an ed25519 based signature management tool. The first implementation wasn't well designed (see git://z3bra.org/sigchk), so I'm rewriting it from scratch, to give it the ability to sign/check streams as well.
As a feature, I'll make signatures base64 encoded too (this will also help me for further development). I'm currently rolling my own base64 encoding/decoding functions as I couldn't find a library that's simple enough for my need. Base64 is simple enough to avoid adding a non-standard dependency.
The rewrite is currently pretty short: http://git.z3bra.org/sick/file/README.html