Cryptology ePrint Archive: Report 2012/631

Message-Locked Encryption and Secure Deduplication

Mihir Bellare and Sriram Keelveedhi and Thomas Ristenpart

Abstract: We formalize a new cryptographic primitive, Message-Locked Encryption (MLE), where the key under which encryption and decryption are performed is itself derived from the message. MLE provides a way to achieve secure deduplication (space-efficient secure outsourced storage), a goal currently targeted by numerous cloud-storage providers. We provide definitions both for privacy and for a form of integrity that we call tag consistency. Based on this foundation, we make both practical and theoretical contributions. On the practical side, we provide ROM security analyses of a natural family of MLE schemes that includes deployed schemes. On the theoretical side the challenge is standard model solutions, and we make connections with deterministic encryption, hash functions secure on correlated inputs and the sample-then-extract paradigm to deliver schemes under different assumptions and for different classes of message sources. Our work shows that MLE is a primitive of both practical and theoretical interest.

Category / Keywords: Convergent encryption, deduplication, deterministic encryption

Publication Info: A preliminary version appears on EUROCRYPT 2013. This is the full version.

Date: received 6 Nov 2012, last revised 11 Mar 2013

Contact author: sriramkr at cs ucsd edu

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Version: 20130311:231700 (All versions of this report)

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