Cryptology ePrint Archive: Report 2017/167

Cloud Storage File Recoverability

Christian A. Gorke and Christian Janson and Frederik Armknecht and Carlos Cid

Abstract: Data loss is perceived as one of the major threats for cloud storage. Consequently, the security community developed several challenge-response protocols that allow a user to remotely verify whether an outsourced file is still intact. However, two important practical problems have not yet been considered. First, clients commonly outsource multiple files of different sizes, raising the question how to formalize such a scheme and in particular ensuring that all files can be simultaneously audited. Second, in case auditing of the files fails, existing schemes do not provide a client with any method to prove if the original files are still recoverable.

We address both problems and describe appropriate solutions. The first problem is tackled by providing a new type of "Proofs of Retrievability" scheme, enabling a client to check all files simultaneously in a compact way. The second problem is solved by defining a novel procedure called "Proofs of Recoverability", enabling a client to obtain an assurance whether a file is recoverable or irreparably damaged. Finally, we present a combination of both schemes allowing the client to check the recoverability of all her original files, thus ensuring cloud storage file recoverability.

Category / Keywords: cryptographic protocols / Proofs of Retrievability, Proofs of Recoverability, Cloud Storage, Cloud Security

Original Publication (with major differences): AsiaCCS-SCC 2017

Date: received 20 Feb 2017, last revised 25 Apr 2017

Contact author: gorke at uni-mannheim de

Available format(s): PDF | BibTeX Citation

Note: Added one related work to Section 2. Added a footnote at the beginning of Section 4.3 to elaborate our choice on SW. Added clarification for the values A and R in Algorithm 2 in Section 5.3. Fixed a typo in Figure 1.

Version: 20170425:154828 (All versions of this report)

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