This page by David Papkin has information on security. All hacking information is for penetration testing and educational purposes only. Please make sure you have signed letter of authorization before doing penetration testing.
OpenID – single sign-on for consumers
SAML – single sign-on for enterprise users
OAuth – API authorization between applications
RADIUS vs TACACS+
|Protocol and Port(s) Used||UDP: 1812 & 1813
-or- UDP: 1645 & 1646
|Encryption||Encrypts only the Password Field||Encrypts the entire payload|