You don't have to give them your private key -- it's just for convenience, if you happen to trust Keybase. You don't have to run it in the browser, either; you

You don't have to give them your private key -- it's just for convenience, if you happen to trust Keybase. You don't have to run it in the browser, either; you can just install the command-line tool via NPM and know exactly what code you're running.