The Google+ Sign-In button bears a striking similarity to the Facebook Login API, and I like that.
The Facebook JS SDK has a signed_request parameter that's provided on the client side but which can be passed to my server, verifying that client-side authentication has taken place. It's cryptographically signed by Facebook, which allows me to verify that the client is logged in without talking to the Facebook on the server side.
Is there a way to do something similar with the G+ JS API? Specifically, I want to do client-side authentication, then POST some data to my server and verify that the client really is logged in to Google, without initiating a server-side request to Google.
(I want this because I only want to use the sign in button as a registration mechanism; I don't want to post to Google Plus or get the user's list of friends or anything like that, which would normally require a full access token.)
So, actually there is a pretty good match for that parameter, the id_token that is returned along with the access_token. It's a signed json web token that includes a userid, the client ID and so on. It sounds like this would address your use case! Take a look at http://android-developers.blogspot.nl/2013/01/verifying-back-end-calls-from-android.html this blog post by Tim Bray - it's Android focused, but the same logic pretty much works for any client.
Once you get this, you know its valid at the point of delivery, just liked a signed_request. Of course in either case if the user signs out or revokes access to your app the access token may no longer be valid for making calls.
Google+ does not make requests to your application on the user's behalf at this time, outside of a callback URL set as part of a vanilla OAuth 2.0 flow.
When receiving a new token or authorization code, you should make the tokeninfo request server-side in order to verify that the token you've received is legitimate, and for the intended user.
I'm not sure which platform your server is using, so I can't paste the relevant code, but please see here for a code sample.
来源：https://stackoverflow.com/questions/15395142/does-google-javascript-api-have-an-equivalent-to-facebooks-signed-request