## Cryptology ePrint Archive: Report 2012/511

Entangled Cloud Storage

Giuseppe Ateniese and Özgür Dagdelen and Ivan Damgard and Daniele Venturi

Abstract: Entangled cloud storage enables a set of clients to entangle'' their files into a single {\em clew} to be stored by a (potentially malicious) cloud provider. The entanglement makes it impossible to modify or delete significant part of the clew without affecting {\em all} files encoded in the clew. A clew keeps the files in it private but still lets each client recover his own data by interacting with the cloud provider; no cooperation from other clients is needed. At the same time, the cloud provider is discouraged from altering or overwriting any significant part of the clew as this will imply that none of the clients can recover their files.

We provide theoretical foundations for entangled cloud storage, introducing the notion of an \emph{entangled encoding scheme} that guarantees strong security requirements capturing the properties above. We also give a concrete construction based on privacy-preserving polynomial interpolation, along with protocols for using the encoding scheme in practice.

Protocols for cloud storage find application in the cloud setting, where clients store their files on a remote server and need to be ensured that the cloud provider will not modify or delete their data illegitimately. Current solutions, e.g., based on Provable Data Possession and Proof of Retrievability, require the server to be challenged regularly to provide evidence that the clients' files are stored \emph{at a given time}. Entangled cloud storage provides an alternative approach where any single client operates implicitly on behalf of all others, i.e., as long as one client's files are intact, the entire remote database continues to be safe and unblemished.

Category / Keywords: cloud storage, multi-party computation

Publication Info: In Submission

Date: received 3 Sep 2012, last revised 14 Feb 2014

Contact author: oezguer dagdelen at cased de

Available format(s): PDF | BibTeX Citation

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