We believe that fundamental to the establishment of a grid computing framework where all (not just large organizations) are able to effectively tap into the resources available on the global network is the establishment of trust between grid application developers and resource donors. Resource donors must be able to trust that their security, safety, and privacy policies will be respected by programs that use their systems. In this paper, we present a novel solution based on the notion of certified code that upholds safety, security, and privacy policies by examining intrinsic properties of code. Certified code complements authentication and provides a foundation for a safe, secure, and efficient framework that executes native code. We describe the implementation of such a framework known as the ConCert software.