Tools for Achieving Usable Ex Post Transparency: A Survey <s> b: DISTRIBUTED SERVICES <s> Transparency is a basic privacy principle and factor of social trust. However, the processing of personal data along a cloud chain is often rather intransparent to the data subjects concerned. Transparency Enhancing Tools (TETs) can help users in deciding on, tracking and controlling their data in the cloud. However, TETs for enhancing privacy also have to be designed to be both privacy-preserving and usable. In this paper, we provide requirements for usable TETs for the cloud. The requirements presented in this paper were derived in two ways; at a stakeholder workshop and through a legal analysis. Here we discuss design principles for usable privacy policies and give examples of TETs which enable end users to track their personal data. We are developing them using both privacy and usability as design criteria. <s> BIB001 </s> Tools for Achieving Usable Ex Post Transparency: A Survey <s> b: DISTRIBUTED SERVICES <s> Location-Based Mobile Service (LBMS) is one of the most popular smartphone services. LBMS enables people to more easily connect with each other and analyze the aspects of their lives. However, sharing location data can leak people's privacy. We present PDVLoc, a controlled location data-sharing framework based on selectively sharing data through a Personal Data Vault (PDV). A PDV is a privacy architecture in which individuals retain ownership of their data. Data are routinely filtered before being shared with content-service providers, and users or data custodian services can participate in making controlled data-sharing decisions. Introducing PDVLoc gives users flexible and granular access control over their location data. We have implemented a prototype of PDVLoc and evaluated it using real location-sharing social networking applications, Google Latitude and Foursquare. Our user study of 19 participants over 20 days shows that most users find that PDVLoc is useful to manage and control their location data, and are willing to continue using PDVLoc. <s> BIB002 </s> Tools for Achieving Usable Ex Post Transparency: A Survey <s> b: DISTRIBUTED SERVICES <s> We present a prototype of the user interface of a transparency tool that displays an overview of a user's data disclosures to different online service providers and allows them to access data collected about them stored at the services' sides. We explore one particular type of visualization method consisting of tracing lines that connect a user's disclosed personal attributes to the service to which these attributes have been disclosed. We report on the ongoing iterative process of design of such visualization, the challenges encountered and the possibilities for future improvements. <s> BIB003
The logging locality of a considerable amount of TETs is distributed among more than a single stakeholder. Many clientsided TETs rely on a remote counterpart to complement local sensing or processing, or to aggregate collected information for further use in a larger context. For example, most of the location sharing TETs fall into this category. While sensing the user's environment and querying the locations of other users is handled by the local client of such TETs, all aggregation and distribution of the collected data to querying parties is taken care of by a central server. The 'Data Track' ('GenomSynlig'), implemented for the A4Cloud EU project BIB003 , logs all data disclosures locally. In addition, it allows users to retrieve transparency logs from remote servers that received and processed their data, and could thus also make transparent data processing along a cloud chain. However, the authors state that the visualisation of remotely logged information has so far not been fully implemented, and is only presented in form of mockups BIB001 . TETs that rely on third-party services are typically designed for large-scale infrastructures that satisfy the demands of a large number of stakeholders. 'PDVLoc' by Mun et al. BIB002 aims at providing a central infrastructure that allows multiple content service providers to query personal data managed by individual data subjects. Conversely, 'Cloudopsy' by Zavou et al.  implements a basic infrastructure that logs transactions of services offered by providers of value-added services. The collected 'audit trails' can be reviewed later by both the providers and the users of these services.