As systems have become interconnected and more complicated, programmers needed ways to identify parties across multiple computers. One way to do this was for the parties that used applications on one computer to authenticate to the applications (and/or operating systems) that ran on the other computers. This mechanism is still widely used-for example, when logging on to a great number of Web sites. However, this approach becomes unmanageable when you have many co-operating systems (as is the case, for example, in the enterprise). Therefore, specialized services were invented that would register and authenticate users, and subsequently provide claims about them to interested applications. Some well-known examples are NTLM, Kerberos, Public Key Infrastructure (PKI), and the Security Assertion Markup Language (SAML). Most enterprise applications need some basic user security features. At a minimum, they need to authenticate their users, and many also need to authorize access to certain...