With the advent of cloud computing, individuals and companies alike are looking for opportunities to leverage cloud resources not only for storage but also for computation. Nevertheless, the reliance on the cloud to perform computation raises the unavoidable challenge of how to assure the correctness of the delegated computation. In this regard, we introduce two cryptographic protocols for publicly verifiable computation that allow a lightweight client to securely outsource to a cloud server the evaluation of highdegree univariate polynomials and the multiplication of large matrices. Similarly to existing work, our protocols follow the amortized verifiable computation approach. Furthermore, by exploiting the mathematical properties of polynomials and matrices, they are more efficient and give way to public delegatability. Finally, besides their efficiency, our protocols are provably secure under wellstudied assumptions.

No abstract

This paper presents StealthGuard, an efficient and provably secure proof of retrievabillity (POR) scheme. StealthGuard makes use of a privacypreserving 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 sentinelbased 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.

No abstract

No abstract