Speeding up LogonUser and sample SSPI code?

[The_Diamond_Z]

I've a service that I'd like to secure calls to. The service speaks to many types of clients over a socket, but for NT clients, I'd like to authenticate against a domain them without requesting a username/password/domain.

Looking around SSPI seems to be just the ticket, but I'm not following the doc's (what can I say, I'm not that bright).

Does anyone have any sample code they're willng to share?

Ideally I'm looking for something like this:

Client:

 pszTokenString = GetInteractiveUsersSecurityToken(...)

Server:

 bool VerifyUsersSecurityToken(pszTokenString)

Alternatively, any other ideas on how to approach this?

Also, I'm using LogonUser to authenticate users that do provide the relevant information. It's a bit slow (almost 2 secs) on our typical enterprise size network. It's the same pool of users that I'll be authenticating each time. Any ideas on how I can speed this up from code? Here's the line of code:

bRet = LogonUser ( NTUserName,
                   NTDomain,
                   pszPassword,
                   LOGON32_LOGON_NETWORK,
                   LOGON32_PROVIDER_DEFAULT,
                   &hLogonHandle);