EDIT: NSA Smiley Face [http://theweek.com/article/index/252034/why-google-isnt-too-...]
The keys are generated by you, stored on your browser's localStorage, preferably encrypted (their words, not mine). Since it's open source and distributed by Google, I bet many eyeballs will look for bugs, much more than alternatives such as Mailvelope or WebPG. So, no, I don't think Google will ever have access to your private key through this mean.
My theory:
- We're talking about PGP. This will only impact geeks.
- Google prefers keeping the trust of said geeks by willingly revoking its capability to read their conversations. One of the primary support of Google success is said geeks, and it wants to keep it that way.
- PGP only encrypts the body of an email. The header (ie the metadata) is still here for Google to collect, in plaintext
Geeks email non-geeks. If the non-geeks don't decrypt the messages it's going to be all greek to them.
So the more easy they make it for geeks, the more they are pushing non-geeks to adopt as well.
That said, pretty much every message I send to someone who doesn't have a key on the keyservers includes, "Hey, send me your PGP key, I don't do plaintext."
Why do people use webmail? Because it's convenient. If I use a client like Thunderbird and download all my emails then if I want to find one of them I have to search for it on the device that I downloaded it. Of course I could upload my emails on a server and access them from other devices but it's a hassle. Webmail solves this problem. Additionally, why competent, smart, technical people very often don't use digital signatures? Same as before plus if you want to use your emails in other devices you have to transfer your secret keys and remember their passphrases.
The transfer of the secret keys is what will keep the usage of this extension low. Therefore, Google succeeds in gaining more trust while offering something that you can already achieve on your own using other software like Thunderbird with the Enigmail extension. Also, note that even by using a digital signature you hide only the emails that you choose to send encrypted and those that you receive encrypted by the senders. I use digital signatures every day, I usually send and receive signed messages. However, the percentage of unencrypted messages in my inbox is probably more than 99%.
So the downside to them is not that big. And it's offset by the upside of user trust and confidence being maintained, or at least eroding less.
It would also get Google a lot of street cred for being a privacy centric business.
My only problem is, I just don't see how you can scale the Chromebook software stack to a privacy centric business. I can't imagine trying to secure PGP keys on a Chromebook. But I haven't used one since the early beta models, so others may have more informed opinions,.