Reliability and Security for Safety-Critical Service Compositions.

Service composition represents the combination of individual distributed services, which are operated by different organizations. A composite service may include security or safety-critical services, which could have a serious impact on individuals and thus, require correctness of generated outputs as a crucial property. For this reason, service composition systems must avoid a manipulation of critical services and have to guarantee high reliability of computed outputs as well as availability. Secure multiparty computation and verifiable secret sharing enables a privacy-preserving computation of service outputs jointly generated by several parties, which makes it possible to prevent a single point of failure for critical services and guarantees correctness of a generated output. In this work, we introduce a concept for privacy-preserving and reliable service compositions through the application of secure multiparty computation in combination with threshold signatures. Threshold signatures make it possible to define a maximum number of allowed unavailable actors, which do not participate in the mulitparty computation protocol. This mechanism enables a flexible definition of security or safety requirements for critical services. The feasibility of the proposed solution is demonstrated by an implemented proof-of-concept for a composite medical alert service.