Re: [tor-dev] File verification GUI tool

Matt Pagan:

If you go the browser extension route, there is a now defunct Firefox add-on called FireGPG that implemented GnuPG in the web browser. This add-on was discontinued in 2010 and it's primary focus was encrypting and decrypting gmail messages. […]

I'd like to remember everyone that it was probably discontinued because in the end it turned to be a terrible idea. Tails wrote a statement about it: https://tails.boum.org/doc/encryption_and_privacy/FireGPG_susceptible_to_devastating_attacks/

Although an extension whose sole purpose would be to verify GnuPG signatures would not have the problem and seems like a good idea. At least, shipping it through addons.mozilla.org give the user some basic trust path.