Explanation/Reference:
The WS-Security specification allows a variety of signature formats, encryption algorithms and multiple trust domains, and is open to various security token models, such as:
* X.509 certificates (not E)
* Kerberos tickets (not D)
*UserID/Password credential (not C)
* SAML Assertions (not B)
* custom-defined tokens.
Note: WS-Security (Web Services Security, short WSS) is a flexible and feature-rich extension to SOAP to apply security to web services. It is a member of the WS-* family of web service specifications and was published by OASIS.