Provide wider overview

[dbosk]

overview is currently quite narrow. The lecture given by Jøsang and Loutfi in Finse is good for inspiratoin.

It should mention Kerberos and anonymous credentials, e.g. Idemix.

[dbosk]

Anonymous credentials is already covered since last year.

[dbosk]

Also discuss using the password as part of the session key, this has improved usability in the sense that users cannot be phished.