Selective End-To-End Data-Sharing in the Cloud

Felix Hörandner, Sebastian Ramacher, Simon Roth

Research output: Chapter in Book/Report/Conference proceedingConference paperpeer-review


Cloud-based services enable easy-to-use data-sharing between multiple parties, and, therefore, have been widely adopted over the last decade. Storage services by large cloud providers such as Dropbox or Google Drive as well as federated solutions such as Nextcloud have amassed millions of users. Nevertheless, privacy challenges hamper the adoption of such services for sensitive data: Firstly, rather than exposing their private data to a cloud service, users desire end-to-end confidentiality of the shared files without sacrificing usability, e.g., without repeatedly encrypting when sharing the same data set with multiple receivers. Secondly, only being able to expose complete (authenticated) files may force users to expose overmuch information. The receivers, as well as the requirements, might be unknown at issue-time, and thus the issued data set does not exactly match those requirements. This mismatch can be bridged by enabling cloud services to selectively disclose only relevant parts of a file without breaking the parts' authenticity. While both challenges have been solved individually, it is not trivial to combine these solutions and maintain their security intentions.

In this paper, we tackle this issue and introduce selective end-to-end data-sharing by combining ideas from proxy re-encryption and redactable signature schemes. Proxy re-encryption provides us with the basis for end-to-end encrypted data-sharing, while redactable signatures enable to redact parts and selectively disclose only the remaining still authenticated parts. We overcome the issues encountered when naively combining these two concepts, introduce a security model, and present a modular instantiation together with implementations based on a selection of various building blocks. We conclude with an extensive performance evaluation of our instantiation.
Original languageEnglish
Title of host publication15th International Conference on Information Systems Security, ICISS 2019
ISBN (Electronic)978-3-030-36945-3
ISBN (Print)978-3-030-36944-6
Publication statusPublished - 2019
Event15th International Conference on Information Systems Security: ICISS 2019 - Hyderabad, India
Duration: 16 Dec 201920 Dec 2019
Conference number: 2019

Publication series

NameLecture Notes in Computer Science
PublisherSpringer, Cham
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349


Conference15th International Conference on Information Systems Security
Abbreviated titleICISS
Internet address


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