Hmac sha-1 hashing algorithm online dating
This one advertised to all subdomains that the user is logged in.
For instance, if you can avoid storing passwords on your server then do it.
Let others do that job for you (Google, Facebook or Twitter).
This is recommended if you are not a security expert.
Maybe you are starting a new online project and want to let your users to login with a social network profile.
By doing this you forget about storing passwords on your server, and despite that all of the previous sites have already been hacked, I am pretty sure that they will have a better understanding of secure password storage.