Tonight I'm in Washington DC with Karen Lewison for the NIST IDTrust workshop, which takes place tomorrow and the day after (April 6-7). We'll be showing a poster on PKAuth, our proposed social login protocol. By social login I mean the buttons that allow you to log in to Web applications with your identity at a social network such as Facebook, LinkedIn or Twitter, giving the application access to your social context at the site. I believe the term social login was coined by Janrain.
Today social login uses the OAuth protocol, which requires prior registration of the application with the social site. The registration process establishes a shared secret that the site later uses to authenticate the application, and provides the site with information that it later uses to identify the application to the user at it asks permission to grant the application access to the user's social context.
The problem with that is that the social site gains the power to disable the application by revoking its registration. Why is that a problem? Because social login is becoming so popular that the day may come when all applications have to register with the dominant social site (currently Facebook) just to be able to authenticate their users. The dominant social site will then have the power to disable any Web application by revoking its registration. That would be bad for users, for applications, and for the dominant social site itself, which would no doubt face registration by multiple governments.
That's why we are proposing PKAuth. In PKAuth registration is optional. A site will be able to require registration for special applications that need, say, administrative access to the user's account, while not requiring it for others. Applications that only want to delegate user authentication should not have to register.
Instead of registration, PKAuth relies on the Web's public key infrastructure, using the application's ordinary SSL certificate to authenticate the application and identify it to the user.
We have just published a revised version of the PKAuth white paper and I will be talking about other benefits of PKAuth in future posts.