The "passport" is just a unique (likely random) string applied to each member account, and is application/server independent, there's no protocol as such.
For example on Oasiz a passport is generated during the very first account connection to the chat server and is made up of an md5 hash of different account fields (ID, account creation date, email address etc) to ensure uniqueness, cut down to 16 digits and capitalised.
Example: 4027E1445E6E24A0
After a successful server authentication this is used as the ident within the hostmask.
<nick>!4027E1445E6E24A0@<host>
Hope this helps!
Edit: I cannot stand this new WYSIWYG editor, it's horrible software.
oasiz got a reaction from Pablo in Gatekeeperpassports