I'm not sure why I'm getting this error form Win2k8 RC0. I can run the sample on Win2k3 without any problems. Do I have to setup some addition security for this to work on Win2k8? Here's the message: Unhandled Exception: System.ServiceModel.Security.MessageSecurityException: An unsecured or incorrectly secured fault was received from the other party. See the inner FaultException for the fault code and detail. ---> System.ServiceModel.FaultException: An error occurred when verifying security for the message. Inner Exception: An error occurred when verifying security for the message. Thomas

The library works without any problem. But when I try to add a namespace prefix like "saml" on the "Assertion" tag, the service can't validate the XML signature. Do I have to add something else ? I have just replaced this line: writer.WriteStartElement(Saml20Constants.Assertion, Saml20Constants.Namespace); with : writer.WriteStartElement(Saml20Constants.NamespacePrefix, Saml20Constants.Assertion, Saml20Constants.Namespace);