Implement a custom authentication scheme by using the System.Security.Authentication classes. (Refer System.Security.Authentication namespace)

• Authentication algorithms and SSL protocols

Another new namespace.  Not much meat there.  I think they're trying to get you to look at the AuthenticatedStream class in System.Net.Security.  Keith Brown has a good example implementation in his "The .NET Developer's Guide to Windows Security"

The algorithms that are implemented appear to be:

NegotiateStream - "Uses the Negotiate security protocol to authenticate the client."  Is there such a thing as the "Negotiate security protocol"?  I'm not finding anything on it.  Sample uses of this class appear to communicating with a server authenticating via Kerberos.

SslStream - "Provides a stream used for client-server communication that uses the Secure Socket Layer (SSL) security protocol to authenticate the server and optionally the client. "  Dominick Baier has a nice simple example.

Next up ->  Cryptography