Cryptology ePrint Archive: Report 2016/621

4-Round Concurrent Non-Malleable Commitments from One-Way Functions

Michele Ciampi and Rafail Ostrovsky and Luisa Siniscalchi and Ivan Visconti

Abstract: How many rounds and which computational assumptions are needed for concurrent non-malleable commitments? The above question has puzzled researchers for several years.

Recently, Pass in [TCC 2013] proved a lower bound of 3 rounds when security is proven through black-box reductions to falsifiable assumptions. On the other side, positive results of Goyal [STOC 2011], Lin and Pass [STOC 2011] and Goyal et al. [FOCS 2012] showed that one-way functions are sufficient with a constant (at least 6) number of rounds. More recently Ciampi et al. [CRYPTO 2016] showed that subexponentially strong one-way permutations are sufficient with just 3 rounds.

In this work we almost close the above open question by showing a 4-round concurrent non-malleable commitment scheme that only needs one-way functions. Our main technique consists in showing how to upgrade basic forms of non-malleability (i.e., non-malleability w.r.t. non-aborting adversaries) to full-fledged non-malleability without penalizing the round complexity.

Category / Keywords: non-malleability, delayed-input protocols

Date: received 14 Jun 2016, last revised 14 Sep 2016

Contact author: ivan visconti at gmail com

Available format(s): PDF | BibTeX Citation

Note: The last revisions fixed some typos and extended the comparison with the state of the art.

Version: 20160915:005511 (All versions of this report)

Short URL: ia.cr/2016/621

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