Can I get a SAP logon ticket in a .NET application?

See more:

.NET

SAP

SSO

Hi,
my application (.NET 4.0) use the SAP dotnet connector (nco 3.0) to communicate with SAP systems. It has his own logon dialog for system, client, username and password.

A new customer of us is using an enterprise portal to work with his SAP systems (using WinShuttle, I hope it doesn't matter). He do a logon at the portal and work with it and he is asking why should he logon again if he use "my" application. He gave me the hint to use spnego.

Now my question:
1. Can I get the SAP logon ticket without any additional logon to the portal, even if I am a own process?
2. If (1. == "yes") can I use this ticket in the nco instead the previous logon credentials?

Thank you in advance for your help