I think that this implements public key encryption for a microblogging service like Twitter. It uses a GPL encryption library but I have not checked the validity of it so: a) use at your own risk b) only use if it's permissible in your country c) can someone check the library and see if it works or not?

I wrote the code purely for research and entertainment purposes. The page itself is published without licence or warranty so you can do whatever you like with it.

Public Key Cryptography for Twitter (et al.)
emetic.co.uk