> So if you’re on Google, you get a doll that says ‘This doll came from Yahoo.’ Then you hand it to the next layer and they open it up and say, ‘This is for Ali

> So if you’re on Google, you get a doll that says ‘This doll came from Yahoo.’ Then you hand it to the next layer and they open it up and say, ‘This is for Alice.’ Then when Alice opens it up, Alice gets the whole message. And where does Alice store her private key? A very large percentage of email users currently use either webmail (e.g. Gmail) or a vendor-provided app (again, Gmail) to access their email. In order for Google to show you the content of your emails in such settings, it needs to be able to open up the last layer. So your private key gets stored on Google's servers, and they can capture your passphrase every time you log in. Remember that Lavabit used your passphrase as the key to your auto-generated private key, which was stored on their servers. This was necessary, not only for compatibility with existing IMAP clients, but also in order for the webmail to work at all. Other companies like Hushmail developed a workaround using Java applets and/or a copious amount of JavaScript cryptography, but all of that is also rubbish because you can't guarantee that they aren't serving you a backdoored version of those scripts. The only way end-to-end security could possibly work in the context of webmail would be for everyone to install a vendor-neutral browser plugin that does all the heavy lifting and that is completely beyond the control of the webpage on which it works (you can't allow the webpage to fetch the decrypted content back into the DOM). But if you're going down that route, you might as well install a standalone email app. It's basically going to be Thunderbird + Enigmail on steroids. Anybody who doesn't want to do that will be stuck keeping their private keys on someone else's machine. Guess what, most users really, really hate having to manage their own keys. tl;dr: This proposal means either the death of webmail as we know it, or little more than an illusion of security.