Cryptology ePrint Archive: Report 2016/977

Side channels in deduplication: trade-offs between leakage and efficiency

Frederik Armknecht and Colin Boyd and Gareth T. Davies and Kristian Gjøsteen and Mohsen Toorani

Abstract: Deduplication removes redundant copies of files or data blocks stored on the cloud. Client-side deduplication, where the client only uploads the file upon the request of the server, provides major storage and bandwidth savings, but introduces a number of security concerns. Harnik et al. (2010) showed how cross-user client-side deduplication inherently gives the adversary access to a (noisy) side-channel that may divulge whether or not a particular file is stored on the server, leading to leakage of user information. We provide formal definitions for deduplication strategies and their security in terms of adversarial advantage. Using these definitions, we provide a criterion for designing good strategies and then prove a bound characterizing the necessary trade-off between security and efficiency.

Category / Keywords: cryptographic protocols / Deduplication, storage,

Date: received 9 Oct 2016, last revised 16 Nov 2016

Contact author: gareth davies at ntnu no

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Version: 20161116:131558 (All versions of this report)

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