StealthGuard: Proofs of Retrievability with Hidden Watchdogs
This paper presents StealthGuard, an efficient and provably secure proof of retrievabillity (POR) scheme. StealthGuard makes use of a privacy-preserving word search (WS) algorithm to search, as part of a POR query, for randomly-valued blocks called watchdogs that are inserted in the file before outsourcing. Thanks to the privacy-preserving features of the WS, neither the cloud provider nor a third party intruder can guess which watchdog is queried in each POR query. Similarly, the responses to POR queries are also obfuscated. Hence to answer correctly to every new set of POR queries, the cloud provider has to retain the file in its entirety. StealthGuard stands out from the earlier sentinel-based POR scheme proposed by Juels and Kaliski (JK), due to the use of WS and the support for an unlimited number of queries by StealthGuard. The paper also presents a formal security analysis of the protocol.
Azraoui M., Elkhiyaoui K., Molva R., Önen M., "StealthGuard: Proofs of Retrievability with Hidden Watchdogs", in Computer Security - ESORICS 2014, Proceedings of 19th European Symposium on Research in Computer Security, Wroclaw, Poland, September 7-11, 2014 (Part I). Lecture Notes in Computer Science Volume 8712, Pages 239-256, Print ISBN 978-3-319-11202-2, Online ISBN 978-3-319-11203-9, Springer International Publishing, DOI: 10.1007/978-3-319-11203-9_14.