I'd like to be able to send people encrypted messages (given I have their public keys which they might give me in a number of ways), when I'm travelling, and don't have a laptop with me but do have a USB that I may have to use on a Mac, Linux or Windows computer wherever I go.
Now for both security and privacy reasons, I don't trust using online web-hosted PGP encrypt / decrypt tools for this purpose, even if their JavaScript code does all the crypto crunching locally in the browser and they promise that they can't see any of the text in the box themselves.
So what would be a reliable, open-source, portable app, (no third-party libraries required on the machine [such as Java], just plug and play), for each of the three main platforms (and ideally the same app from the same project), to do this?