47
<Response xmlns="urn:oasis:names:tc:SAML:2.0:protocol"
                  ID="fff011234"
                  InResponseTo="abe567de6"
                  Version="2.0"
                  IssueInstant="2005-01-31T12:00:00Z"
                  Destination="https://www.CarRentalInc.com">
      ...
</Response>
<AuthnRequest xmlns="urn:oasis:names:tc:SAML:2.0:protocol"
                         ForceAuthn="true"
                         ProviderName="CarRentalInc.com"
                         ID="abe567de6"
                         Version="2.0"
                         IssueInstant="2005-01-31T11:58:00Z"
                          Destination="https://www.AirlineInc.com">
      ...
</AuthnRequest>
InResponseTo must match up
with the ID in the AuthnRequest
messsage