Protecting RESTful WCF with Tokens in HTTP Headers

Question

Protecting RESTful WCF with Tokens in HTTP Headers

I am working on creating a WCF RESTful service that will be protected by passing external authentication tokens in HTTP headers. So the sequence looks like this:

Client: get authentication token from authentication server
Client: construct REST host authentication token in a custom HTTP header
Client: run the command
Stop server: check for authentication token
Break server: request authentication server to check token and get user context
Stop Server: User Authorization Rest Server: Performing a Service Action

So my question is the best way to do this in WCF / .NET? I could of course handle authentication / authorization in my REST method, i.e.

public void DoSomething(string input)
{
    if (Authed())
    {
        ...Do DoSomething...
    }
    else
    {
        throw new FaultException<MyFault>(new MyFault("Not today, thanks"));
    }
}

public bool Authed()
{
    string rawUserAuthToken = WebOperationContext.Current.IncomingRequest.Headers["MyCustomHttpHeader"];

    ...Do the magic needed to verify and Authorise the incoming token...

    return result;
}