Trustworthy Privacy-Preserving Service Compositions

E-Government applications are often composed of services provided by multiple service providers. Thus, public services must ensure accountability of performed actions to increase the trust in electronic services. Trust is crucial for user satisfaction and represents a key factor for the success of public services. Accountability is also necessary to determine an unintended behaviour of participants in service compositions. Transparent monitoring systems can facilitate the detection of failures or malicious behaviour of attackers. However, the demand for more accountability and transparency in public services arises challenges regarding the privacy of citizen's data. In this paper we propose a service composition concept providing accountability of service providers and considering privacy of sensitive data. This composition system uses proxy re-encryption in the communication protocol and cryptographically chains executed transactions. Retrospectively, citizens as well as participants of a processed service can validate the chained transactions. An implemented proof-of-concept demonstrates the feasibility of the proposed solution, which clearly supports accountability and thus increases trust in public services among citizens.