The first part of the paper describes the design of a service module that assists customers with the leasing of cloud computing services by taking into account their require- ments on service provisioning. The service module introduces basic service level management functionality within a larger framework. The framework is illustrated as a web platform and uses a trusted third party (TTP) as a secure middle layer on service transactions. The second part of the paper focuses on the TTP role. Preliminary security requirements are identified and analyzed for the implementation and successful operation of such a TTP entity.