Cryptology ePrint Archive: Report 2018/422

Message-locked Encryption with File Update

Suyash Kandele and Souradyuti Paul

Abstract: Message-locked encryption (MLE) (formalized by Bellare, Keelveedhi and Ristenpart, 2013) is an important cryptographic primitive that supports deduplication in the cloud. Updatable block-level message-locked encryption (UMLE) (formalized by Zhao and Chow, 2017) adds the update functionality to the MLE. In this paper, we formalize and extensively study a new cryptographic primitive file-updatable message-locked encryption (FMLE). FMLE can be viewed as a generalization of the UMLE, in the sense that unlike the latter, the former does not require the existence of BL-MLE (block-level message-locked encryption). FMLE allows more flexibility and efficient methods for updating the ciphertext and tag. Our second contribution is the design of two efficient FMLE constructions, namely, RevD-1 and RevD-2, whose design principles are inspired from the very unique reverse decryption functionality of the FP hash function (designed by Paul, Homsirikamol and Gaj, 2012) and the APE authenticated encryption (designed by Andreeva et al., 2014). With respect to UMLE which provides so far the most efficient update function RevD-1 and RevD-2 reduce the total update time by at least 50%, on average. Additionally, our constructions are storage efficient. We also give extensive comparison between our and the existing constructions.

Category / Keywords: cryptographic protocols / Message-locked encryption, symmetric key cryptography, hash mode of operation

Original Publication (with major differences): Applied Cryptography and Network Security (ACNS) 2018

Date: received 8 May 2018

Contact author: suyashk at iitbhilai ac in

Available format(s): PDF | BibTeX Citation

Version: 20180510:205613 (All versions of this report)

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