Authorization as a service in smart grids: Evaluating the PaaS paradigm for XACML policy decision points

This paper introduces an architecture offering authorization as a service for smart grids environments founding on the two standards XACML and SAML. A software prototype is deployed with the Platform as a Service (PaaS) framework Appscale. Appscale is an open source implementation of Google´s App Engine framework enabling the execution of applications in a cloud environment without the need to take care of the issues arising out of the distributed computing model. Evaluation of the prototype focuses on its scalability. Load tests are run against the system in various configurations with all distributed databases offered by Appscale. The recorded results are ranging from a very unstable behavior to the awaited scalability dependent on the number of nodes used for App-scale deployment.