### Fully Deniable Interactive Encryption

Ran Canetti, Sunoo Park, and Oxana Poburinnaya

##### Abstract

Deniable encryption (Canetti et al., Crypto 1996) enhances secret communication over public channels, providing the additional guarantee that the secrecy of communication is protected even if the parties are later coerced (or willingly bribed) to expose their entire internal states: plaintexts, keys and randomness. To date, constructions of deniable encryption --- and more generally, interactive deniable communication --- only address restricted cases where only one party is compromised (Sahai and Waters, STOC 2014). The main question --- whether deniable communication is at all possible if both parties are coerced at once --- has remained open. We resolve this question in the affirmative, presenting a communication protocol that is fully deniable under coercion of both parties. Our scheme has three rounds, assumes subexponentially secure indistinguishability obfuscation and one-way functions, and uses a short global reference string that is generated once at system set-up and suffices for an unbounded number of encryptions and decryptions. Of independent interest, we introduce a new notion called off-the-record deniability, which protects parties even when their claimed internal states are inconsistent (a case not covered by prior definitions). Our scheme satisfies both standard deniability and off-the-record deniability.

Note: The paper has been significantly revised. The introduction and technical overview has been completely rewritten. A proof of security in the oracle-access model was added.

Available format(s)
Category
Cryptographic protocols
Publication info
A major revision of an IACR publication in CRYPTO 2020
Keywords
deniable encryption
Contact author(s)
oxanapob @ bu edu
sunoo @ csail mit edu
canetti @ bu edu
History
2020-07-25: last of 4 revisions
See all versions
Short URL
https://ia.cr/2018/1244

CC BY

BibTeX

@misc{cryptoeprint:2018/1244,
author = {Ran Canetti and Sunoo Park and Oxana Poburinnaya},
title = {Fully Deniable Interactive Encryption},
howpublished = {Cryptology ePrint Archive, Paper 2018/1244},
year = {2018},
note = {\url{https://eprint.iacr.org/2018/1244}},
url = {https://eprint.iacr.org/2018/1244}
}

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