A method for mutual authorization of a secondary resource in a grid of resource computers is provided. When a primary resource attempts to offload a grid computing job to a secondary resource, the primary resource sends a proxy certificate request to the user machine. Responsive to a proxy certificate request, the user machine performs authorization with the secondary resource. If authorization with the secondary resource is successful, the user machine generates and returns a valid proxy certificate. The primary resource then performs mutual authentication with the secondary resource. If the authorization with the secondary resource fails, the user machine generates and returns an invalid proxy certificate. Mutual authentication between the primary resource and the secondary resource will fail due to the invalid proxy certificate. The primary resource then selects another secondary resource and repeats the process until a resource is found that passes the mutual authorization with the user machine.