The D-Grid community project C3-Grid is in the process of building a Grid testbed with Shibboleth-based authentication und authorization. This testbed utilizes GridSphere, Globus Toolkit and metadata mechanisms specific to C3-Grid. Shibboleth will be integrated by way of GridShib's solution proposal for Teragrid Science Gateways. It shall be shown that portal-generated proxy certificates with embedded SAML statements, asserted by distributed Identity Providers, may be used for resource authorization in a production grid. Building blocks and the roadmap for this approach are presented.