Insynd: Improved Privacy-Preserving Transparency Logging

Abstract

Abstract. Service providers collect and process more user data then ever, while users of these services remain oblivious to the actual processing and utility of the processed data to the service providers. This leads users to put less trust in service providers and be more reluctant to share data. Transparency logging is about service providers continuously logging descriptions of the data processing on their users' data, where each description is intended for a particular user. We propose Insynd, a new cryptographic scheme for privacy-preserving transparency logging. Insynd improves on prior work by (1) increasing the utility of all data sent through the scheme thanks to our publicly verifiable proofs: one can disclose selected events without having to disclose any long term secrets; and (2) enabling a stronger adversarial model: Inysnd can deal with an untrusted server (such as commodity cloud services) through the use of an authenticated data structure named Balloon. Finally, our publicly available prototype implementation shows greatly improved performance with respect to related work and competitive performance for more data-intensive settings like secure logging.

An Overview of Runtime Data Protection Enforcement Approaches

“…Informed privacy settings [35] Consent Management Platforms [36]- [38] Privacy nudges [39]- [42] Data Management Data minimization [24] De-identification [43] Differential privacy [44] Local differential privacy [45] Compliant database [46] Policies P3P [47], [48] Enterprise privacy policies [49] Sticky policies [50]- [52] Access Control (Data User) [53], [54] Access Control (Data Subject) [55] Privacy API [56] Monitoring Minimization monitoring [57] Logging [58]- [60] Workflow auditing [61] Legend: D design time decision, R runtime decision, primary principle the technology contributes to (not necessarily complete so other technologies can still be required), other principles the technology can contribute to.…”

Transparency Enhancing Technologies to Make Security Protocols Work for Humans

“…A prefix tree and a history tree can be combined into a single system to form a verifiable log-backed map [8], [83] (see also Key Transparency [82] and the proposed enhanced certificate transparency [163]). (The prefix tree can alternatively be a hash treap [151], [156]. )…”

Certificate Transparency with Privacy

“…Extended Certificate Transparency [43] adds a second log to efficiently handle certificate revocation and presents an application to secure email. Finally, a number of works have focused on building general transparent data structures and enabling computation over them [40,41,37,49].…”