However, regardless of the application setting with oneor more data resources, in many cases, data are privacy sensitive or commercially valuable: the data owners might not want to reveal their sensitive data to the service provider, for instance in social networks, as the data can be processed for other purposes, transferred to other third parties without user consent or stolen by outsiders. In the case of multiple data resources from different entities as in banking, the data owners might not want to take risks in sharing their customer data with other competitors. Clearly, such privacy-related concerns might result in severa drawbacks: people not joining social networks or database owners preferring to process data on their own.