Send credentials/user information accross applcations securely?

[Guest]

I have three separate applications setup on an IIS server. Let’s call them
AppA, AppB, and AppC. On AppA (the Default application) the user is presented
with a login window. The login information is stored in a SQL Database.
Depending on the user’s credentials they can be routed to AppB or AppC. I
need to securely pass the user’s login name and unique identifier to either
AppB or AppC. How can I, in ASP.NET, securely pass this information to the
applications? I can send the information in the query string, but I don’t
know how to secure this. Can I use a web service and the
System.Security.Cryptography class? Any help is appreciated.

Daniel C. Di Vita