The difference between Spring Security LDAP VS CAS VS OpenID

Question

In spring security I understand that there are different modules catered to different usage and among some of the modules I saw LDAP, CAS and OPENID.

From my understanding

1. CAS - it is only used for authentication purposes based on a SSO
2. LDAP - it is based on a LDAP server to authenticate users and manage them. Am I correct?
3. OPENID - It is also based on a OpenID Server to authenticate users

If that is the case, why would some people use CAS instead of LDAP? Maybe it is because of different usability? Can anyone shed the difference between the 3 of them why are one more preferred than the others?

Answer 1

CAS as a protocol is a mechanism to provide web single signon. There is also CAS, the software platform that implements that protocol amongst many others, including openid.

OpenId is also an authentication protocol, similar to CAS, able to achieve web single sign on but more in a federated fashion.

LDAP is a protocol that defines how one should talk to a directory server. Most systems use LDAP to talk to a directory to retrieve user accounts, verify them and retrieve attributes associated with them. It has nothing to do with authentication or single sign on. CAS, the software, can be configured to find user accounts from ldap, find attributes from ldap or do other things with ldap.