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{{short description|Encryption techniques where an adversary cannot prove that the plaintext data exists}}{{Multiple issues|{{Primary sources|date=March 2024}}
{{Needs additional citations|date=March 2024}}}}

In [[cryptography]] and [[steganography]], plausibly '''deniable encryption''' describes [[encryption]] techniques where the existence of an encrypted file or message is deniable in the sense that an adversary cannot prove that the [[plaintext]] data exists.<ref>See http://www.schneier.com/paper-truecrypt-dfs.html {{Webarchive|url=https://web.archive.org/web/20140627184940/https://www.schneier.com/paper-truecrypt-dfs.html |date=2014-06-27 }}. Retrieved on 2013-07-26.</ref>

The users may [[plausible deniability|convincingly deny]] that a given piece of data is encrypted, or that they are able to decrypt a given piece of encrypted data, or that some specific encrypted data exists.<ref name=":1">{{Cite journal |last1=Chen |first1=Chen |last2=Chakraborti |first2=Anrin |last3=Sion |first3=Radu |date=2020 |title=INFUSE: Invisible plausibly-deniable file system for NAND flash |url=https://petsymposium.org/popets/2020/popets-2020-0071.php |url-status=live |journal=Proceedings on Privacy Enhancing Technologies |volume=2020 |issue=4 |pages=239–254 |doi=10.2478/popets-2020-0071 |issn=2299-0984 |archive-url=https://web.archive.org/web/20230208113349/https://petsymposium.org/popets/2020/popets-2020-0071.php |archive-date=2023-02-08 |access-date=2024-04-02 |doi-access=free}}</ref> Such denials may or may not be genuine. For example, it may be impossible to prove that the data is encrypted without the cooperation of the users. If the data is encrypted, the users genuinely may not be able to decrypt it. Deniable encryption serves to undermine an attacker's confidence either that data is encrypted, or that the person in possession of it can decrypt it and provide the associated plaintext.

In their pivotal 1996 paper, [[Ran Canetti]], [[Cynthia Dwork]], [[Moni Naor]], and [[Rafail Ostrovsky]] introduced the concept of deniable encryption, a cryptographic breakthrough that ensures privacy even under coercion. This concept allows encrypted communication participants to plausibly deny the true content of their messages. Their work lays the foundational principles of deniable encryption, illustrating its critical role in protecting privacy against forced disclosures. This research has become a cornerstone for future advancements in cryptography, emphasizing the importance of deniable encryption in maintaining communication security.<ref name=":0">{{cite book |author=Ran Canetti, Cynthia Dwork, Moni Naor, [[Rafail Ostrovsky]] |title=Advances in Cryptology – CRYPTO '97 |date=1996-05-10 |isbn=978-3-540-63384-6 |series=Lecture Notes in Computer Science |volume=1294 |pages=90&ndash;104 |chapter=Deniable Encryption |doi=10.1007/BFb0052229 |chapter-url=http://eprint.iacr.org/1996/002 |chapter-format=PostScript |archive-url=https://web.archive.org/web/20200824164510/https://eprint.iacr.org/1996/002 |archive-date=2020-08-24 |url-status=live |accessdate=2007-01-05}}</ref> The notion of deniable encryption was used by [[Julian Assange]] and [[Ralf Weinmann]] in the Rubberhose filesystem.<ref>See {{cite web |title=Rubberhose cryptographically deniable transparent disk encryption system |url=http://iq.org/~proff/rubberhose.org/ |url-status=dead |archive-url=https://web.archive.org/web/20100915130330/http://iq.org/~proff/rubberhose.org/ |archive-date=2010-09-15 |accessdate=2010-10-21}}. Retrieved on 2009-07-22.</ref><ref name=":1" />

==Function==
Deniable encryption makes it impossible to prove the origin or existence of the plaintext message without the proper decryption key. This may be done by allowing an encrypted message to be decrypted to different sensible plaintexts, depending on the [[Key (cryptography)|key]] used. This allows the sender to have [[plausible deniability]] if compelled to give up their encryption key.

===Scenario===
In some jurisdictions, statutes assume that human operators have access to such things as encryption keys, and governments may enact [[key disclosure law]]s that compel individuals to relinquish keys upon request. Countries such as [[France]]<ref>Articles 30–31, {{cite French law|number or usual name=n<sup>o</sup> 2001-1062|date in French=15 novembre 2001|full name=relative à la sécurité quotidienne|language=French|lower case=yes|URL=http://www.legifrance.gouv.fr/affichTexte.do?cidTexte=JORFTEXT000000222052}}</ref> and [[Australia]]<ref>{{cite act |title=Cybercrime Act 2001 |at=ords 12, 28 |location=Cth |italics=y |url=https://rm.coe.int/cybercrime-act-2001/16808e70b4 |access-date=2025-05-31 |date=2004-09-06}}</ref> give prosecutors wide-ranging power to compel any person to surrender keys to make available any information encountered in the course of an investigation, and failure to comply incurs jail time and/or civil fines. Another example is the [[United Kingdom]]'s [[Regulation of Investigatory Powers Act 2000|Regulation of Investigatory Powers Act]],<ref name="Guardian Q&As">{{cite news |date=October 25, 2001 |title=The RIP Act |url=https://www.theguardian.com/world/2000/oct/24/qanda |work=[[The Guardian]] |location=London |access-date=March 19, 2024 |archive-date=March 28, 2023 |archive-url=https://web.archive.org/web/20230328104031/https://www.theguardian.com/world/2000/oct/24/qanda |url-status=live }}</ref><ref name="RIP online">{{cite web |date=9 May 2000 |title=Regulation of Investigatory Powers Bill; in Session 1999-2000, Internet Publications, Other Bills before Parliament |url=http://www.parliament.the-stationery-office.co.uk/pa/ld199900/ldbills/061/2000061.htm |url-status=dead |archive-url=https://web.archive.org/web/20111108020103/http://www.parliament.the-stationery-office.co.uk/pa/ld199900/ldbills/061/2000061.htm |archive-date=8 November 2011 |access-date=5 Jan 2011 |publisher=House of Lords}}</ref> which makes it a crime not to surrender [[Key (cryptography)|encryption keys]] on demand from a government official authorized by the act. According to the [[Home Office]], the burden of proof that an accused person is in possession of a key rests on the prosecution; moreover, the act contains a defense for operators who have lost or forgotten a key, and they are not liable if they are judged to have done what they can to recover a key.<ref name="Guardian Q&As" /><ref name="RIP online" /> Such laws are not universal, however - in the [[United States]], though the issue has never reached the [[Supreme Court of the United States|Supreme Court]], lower courts frequently view forced disclosure of [[password]]s as a form of [[self-incrimination]] and an unconstitutional abridgement of the [[Fifth Amendment to the United States Constitution|Fifth Amendment]].<ref>{{cite court |litigants=In RE: GRAND JURY SUBPOENA DUCES TECUM |opinion=Nos. 11-12268 & 11-15421 |court=11th Cir. |date=2012-02-23 |url=https://media.ca11.uscourts.gov/opinions/pub/files/201112268.pdf |quote=We hold that Doe properly invoked the Fifth Amendment privilege. In response, the Government chose not give him the immunity the Fifth Amendment and 18 U.S.C. § 6002 mandate, and the district court acquiesced. Stripped of Fifth Amendment protection, Doe refused to produce the unencrypted contents of the hard drives. The refusal was justified, and the district court erred in adjudging him in civil contempt. The district court’s judgment is accordingly REVERSED. }}</ref><ref>{{cite court |litigants=U.S. v Jeffrey Feldman |vol=THE DECRYPTION OF A SEIZED DATA STORAGE SYSTEM |court=E.D. Wis. |date=19 April 2013 |url=https://www.wired.com/images_blogs/threatlevel/2013/04/encryption-case.pdf |access-date=24 April 2013 |archive-url=https://web.archive.org/web/20210322102931/https://www.wired.com/images_blogs/threatlevel/2013/04/encryption-case.pdf |url-status=live }}</ref><ref>{{Cite web |title=State Court Docket Watch: State of Oregon v. Pittman |url=https://fedsoc.org/commentary/publications/state-court-docket-watch-state-of-oregon-v-pittman |access-date=2022-03-10 |website=fedsoc.org |date=23 April 2021 |archive-date=2021-06-05 |archive-url=https://web.archive.org/web/20210605152818/https://fedsoc.org/commentary/publications/state-court-docket-watch-state-of-oregon-v-pittman |url-status=live }}</ref>

{{anchor|rubber}}In [[cryptography]], [[rubber-hose cryptanalysis]] is a [[euphemism]] for the extraction of cryptographic secrets (e.g. the password to an encrypted file) from a person by [[coercion]] or [[torture]]<ref>{{cite web |last=Schneier |first=Bruce |author-link=Bruce Schneier |date=October 27, 2008 |title=Rubber-Hose Cryptanalysis |url=http://www.schneier.com/blog/archives/2008/10/rubber_hose_cry.html |access-date=August 29, 2009 |work=Schneier on Security |archive-date=August 30, 2009 |archive-url=https://web.archive.org/web/20090830073523/http://www.schneier.com/blog/archives/2008/10/rubber_hose_cry.html |url-status=live }}</ref>—such as beating that person with a rubber [[hose]], hence the name—in contrast to a mathematical or technical [[Cryptanalysis|cryptanalytic attack]]. An early use of the term was on the [[sci.crypt]] newsgroup, in a message posted 16 October 1990 by [[Marcus J. Ranum]], alluding to [[Foot whipping|corporal punishment]]:<blockquote>...the rubber-hose technique of cryptanalysis. (in which a rubber hose is applied forcefully and frequently to the soles of the feet until the key to the cryptosystem is discovered, a process that can take a surprisingly short time and is quite computationally inexpensive).<ref>{{cite newsgroup |url=http://groups.google.com/group/sci.crypt/msg/86404637e708d900?pli=1 |title=Re: Cryptography and the Law... |first=Marcus J. |last=Ranum |newsgroup=sci.crypt |message-id=1990Oct16.050000.4965@decuac.dec.com |date=October 16, 1990 |access-date=October 11, 2013 |archive-date=April 2, 2024 |archive-url=https://web.archive.org/web/20240402041852/https://groups.google.com/g/sci.crypt/c/W1VUQlC99LM/m/ANkI5zdGQIYJ?pli=1 |url-status=live }}</ref></blockquote> Such methods are also euphemistically referred to as "wrench attacks," in reference to an [[xkcd]] comic with a similar premise.<ref>{{cite web |url=https://apnews.com/article/crypto-bitcoin-kidnapping-wrench-attack-ddc7263c25ba590f85648e1682576971 |title=Why 'wrench attacks' on wealthy crypto holders are on the rise |last=Suderman |first=Alan |publisher=[[Associated Press]] |date=2025-05-28 }}</ref><ref>{{cite journal |title=Investigating Wrench Attacks: Physical Attacks Targeting Cryptocurrency Users |journal=6th Conference on Advances in Financial Technologies |year=2024 |last1=Ordekian |first1=Marilyne |last2=Atondo-Siu |first2=Gilberto |last3=Hutchings |first3=Alice |last4=Vasek |first4=Marie |series=Leibniz International Proceedings in Informatics (LIPIcs) |volume=316 |pages=24:1–24:24 |issn=1868-8969 |doi=10.4230/LIPIcs.AFT.2024.24 |url=https://drops.dagstuhl.de/storage/00lipics/lipics-vol316-aft2024/LIPIcs.AFT.2024.24/LIPIcs.AFT.2024.24.pdf |access-date=2025-05-31 |publisher=[[Dagstuhl#Leibniz-Zentrum für Informatik|Schloss Dagstuhl – Leibniz-Zentrum für Informatik]] |doi-access=free |isbn=978-3-95977-345-4 }}</ref>

Deniable encryption allows the sender of an encrypted message to deny sending that message. This requires a [[trusted third party]]. A possible scenario works like this:

#Bob suspects his wife [[Alice and Bob|Alice]] is engaged in adultery. That being the case, Alice wants to communicate with her secret lover Carl. She creates two keys, one intended to be kept secret, the other intended to be sacrificed. She passes the secret key (or both) to Carl.
#Alice constructs an innocuous message M1 for Carl (intended to be revealed to Bob in case of discovery) and an incriminating love letter M2 to Carl. She constructs a cipher-text C out of both messages, M1 and M2, and emails it to Carl.
#Carl uses his key to decrypt M2 (and possibly M1, in order to read the fake message, too).
#Bob finds out about the email to Carl, becomes suspicious and forces Alice to decrypt the message.
#Alice uses the sacrificial key and reveals the innocuous message M1 to Bob. Since it is impossible for Bob to know for sure that there might be other messages contained in C, he might assume that there ''are'' no other messages.

Another scenario involves Alice sending the same ciphertext (some secret instructions) to Bob and Carl, to whom she has handed different keys. Bob and Carl are to receive different instructions and must not be able to read each other's instructions. Bob will receive the message first and then forward it to Carl.

#Alice constructs the ciphertext out of both messages, M1 and M2, and emails it to Bob.
#Bob uses his key to decrypt M1 and isn't able to read M2.
#Bob forwards the ciphertext to Carl.
#Carl uses his key to decrypt M2 and isn't able to read M1.

==Forms of deniable encryption==
Normally, ciphertexts decrypt to a single plaintext that is intended to be kept secret. However, one form of deniable encryption allows its users to decrypt the ciphertext to produce a different (innocuous but plausible) plaintext and plausibly claim that it is what they encrypted. The holder of the ciphertext will not be able to differentiate between the true plaintext, and the bogus-claim plaintext. In general, one [[ciphertext]] cannot be decrypted to all possible [[plaintext]]s unless the key is as large as the [[plaintext]], so it is not practical in most cases for a ciphertext to reveal no information whatsoever about its plaintext.<ref>{{cite journal| last=Shannon| first=Claude| title=Communication Theory of Secrecy Systems| journal=Bell System Technical Journal| volume=28| issue=4| pages=659–664| year=1949| doi=10.1002/j.1538-7305.1949.tb00928.x| url=https://www.cs.virginia.edu/~evans/greatworks/shannon1949.pdf| access-date=2022-01-14| archive-date=2022-01-14| archive-url=https://web.archive.org/web/20220114040422/https://www.cs.virginia.edu/~evans/greatworks/shannon1949.pdf| url-status=live}}</ref> However, some schemes allow decryption to decoy plaintexts that are close to the original in some metric (such as [[edit distance]]).<ref>{{cite conference
| url=https://www.blackhat.com/docs/asia-14/materials/Trachtenberg/WP-Asia-14-Trachtenberg-Say-It-Ain%27t-So-An-Implementation-Of-Deniable-Encryption.pdf
| title=Say it Ain't So - An Implementation of Deniable Encryption
| first=Ari
| last=Trachtenberg
| date=March 2014
| conference=Blackhat Asia
| conference-url=https://www.blackhat.com/asia-14/
| location=Singapore
| access-date=2015-03-06
| archive-date=2015-04-21
| archive-url=https://web.archive.org/web/20150421042044/https://www.blackhat.com/docs/asia-14/materials/Trachtenberg/WP-Asia-14-Trachtenberg-Say-It-Ain%27t-So-An-Implementation-Of-Deniable-Encryption.pdf
| url-status=live
}}</ref>

Modern deniable encryption techniques exploit the fact that without the key, it is infeasible to distinguish between ciphertext from [[block cipher]]s and data generated by a [[cryptographically secure pseudorandom number generator]] (the cipher's [[pseudorandom permutation]] properties).<ref>{{cite book
| title=Cryptographic Engineering
| first1=Debrup
| last1=Chakraborty
| first2=Francisco
| last2=Rodríguez-Henríquez.
| editor=Çetin Kaya Koç
| url=https://books.google.com/books?id=nErZY4vYHIoC&q=%22she+should+be+unable+to+distinguish+those+plaintexts%22&pg=PA340
| year=2008
| page=340
| publisher=Springer
| isbn=9780387718170
| access-date=2020-11-18
| archive-date=2024-04-02
| archive-url=https://web.archive.org/web/20240402041852/https://books.google.com/books?id=nErZY4vYHIoC&q=%22she+should+be+unable+to+distinguish+those+plaintexts%22&pg=PA340#v=snippet&q=%22she%20should%20be%20unable%20to%20distinguish%20those%20plaintexts%22&f=false
| url-status=live
}}</ref>

This is used in combination with some [[decoy]] data that the user would plausibly want to keep confidential that will be revealed to the attacker, claiming that this is all there is. This is a form of [[steganography]].{{Cn|date=March 2024}}

If the user does not supply the correct key for the truly secret data, decrypting it will result in apparently random data, indistinguishable from not having stored any particular data there.{{Cn|date=March 2024}}

=== Examples ===

==== Layers ====
One example of deniable encryption is a [[cryptographic filesystem]] that employs a concept of abstract "layers", where each layer can be decrypted with a different encryption key.{{Cn|date=March 2024}} Additionally, special "[[chaff (radar countermeasure)|chaff]] layers" are filled with random data in order to have [[plausible deniability]] of the existence of real layers and their encryption keys.{{Cn|date=March 2024}} The user can store decoy files on one or more layers while denying the existence of others, claiming that the rest of space is taken up by chaff layers.{{Cn|date=March 2024}} Physically, these types of filesystems are typically stored in a single directory consisting of equal-length files with filenames that are either [[randomness|random]]ized (in case they belong to chaff layers), or [[cryptographic hash function|cryptographic hash]]es of strings identifying the blocks.{{Cn|date=March 2024}} The [[timestamp]]s of these files are always randomized.{{Cn|date=March 2024}} Examples of this approach include Rubberhose filesystem. 

Rubberhose (also known by its development codename Marutukku)<ref name="dreyfus">{{cite web |title=Rubberhose cryptographically deniable transparent disk encryption system |url=http://marutukku.org/ |url-status=dead |archive-url=https://web.archive.org/web/20120716034441/http://marutukku.org/ |archive-date=16 July 2012 |access-date=12 January 2022 |website=marutukku.org}}</ref> is a deniable encryption program which encrypts data on a storage device and hides the encrypted data. The existence of the encrypted data can only be verified using the appropriate cryptographic key. It was created by [[Julian Assange]] as a tool for human rights workers who needed to protect sensitive data in the field and was initially released in 1997.<ref name="dreyfus" /> 

The name Rubberhose is a joking reference to the [[cypherpunks]] term rubber-hose cryptanalysis, in which encryption keys are obtained by means of violence.{{Cn|date=March 2024}} 

It was written for [[Linux kernel]] 2.2, [[NetBSD]] and [[FreeBSD]] in 1997–2000 by [[Julian Assange]], [[Suelette Dreyfus]], and Ralf Weinmann. The latest version available, still in alpha stage, is v0.8.3.<ref name="marutukku">{{cite web |title=Rubberhose cryptographically deniable transparent disk encryption system |url=http://marutukku.org/ |url-status=dead |archive-url=https://web.archive.org/web/20120716034441/http://marutukku.org/ |archive-date=16 July 2012 |access-date=12 January 2022 |website=marutukku.org}}</ref>

==== Container volumes ====
Another approach used by some conventional [[disk encryption software]] suites is creating a second encrypted [[volume (computing)|volume]] within a container volume. The container volume is first formatted by filling it with encrypted random data,<ref name="LibreCrypt">{{Cite web| url=https://github.com/t-d-k/LibreCrypt/blob/master/docs/plausible_deniability.md| title=LibreCrypt: Transparent on-the-fly disk encryption for Windows. LUKS compatible.: T-d-k/LibreCrypt| website=[[GitHub]]| date=2019-02-09| access-date=2015-07-03| archive-date=2019-12-15| archive-url=https://web.archive.org/web/20191215031303/https://github.com/t-d-k/LibreCrypt/blob/master/docs/plausible_deniability.md| url-status=live}}</ref> and then initializing a filesystem on it. The user then fills some of the filesystem with legitimate, but plausible-looking decoy files that the user would seem to have an incentive to hide. Next, a new encrypted volume (the hidden volume) is allocated within the free space of the container filesystem which will be used for data the user actually wants to hide. Since an adversary cannot differentiate between encrypted data and the random data used to initialize the outer volume, this inner volume is now undetectable. [[LibreCrypt]]<ref name=LibreCrypt-plausible-deniability>{{cite web |title=LibreCrypt documentation on Plausible Deniability |website=[[GitHub]] |url=https://github.com/t-d-k/LibreCrypt/blob/master/docs/plausible_deniability.md |date=2019-02-09 |access-date=2015-07-03 |archive-date=2019-12-15 |archive-url=https://web.archive.org/web/20191215031303/https://github.com/t-d-k/LibreCrypt/blob/master/docs/plausible_deniability.md |url-status=live }}</ref> and [[BestCrypt]] can have many hidden volumes in a container; [[TrueCrypt]] is limited to one hidden volume.<ref name="truecrypt.org">{{Cite web | url=http://www.truecrypt.org/hiddenvolume | title=TrueCrypt | access-date=2006-02-16 | archive-date=2012-09-14 | archive-url=https://archive.today/20120914151319/http://www.truecrypt.org/hiddenvolume | url-status=live }}</ref>

==== Other software ====
*[[Cryptee]], an [[open-source]], [[Client-Side Encryption|client-side encrypted]], [[Cross-platform software|cross-platform]] [[Productivity software|productivity suite]] and [[File-hosting service|cloud storage service]] which offers its users the ability to hide (''ghost'') folders and photo albums for [[plausible deniability#Use_in_cryptography|plausible deniability]].

*[[LibreCrypt]], [[open-source]] [[Disk encryption|transparent disk encryption]] for MS Windows and PocketPC PDAs that provides both deniable encryption and [[plausible deniability]].<ref name="LibreCrypt" /><ref>See its [https://github.com/t-d-k/LibreCrypt/blob/master/docs/plausible_deniability.md documentation section on "Plausible Deniability"] {{Webarchive|url=https://web.archive.org/web/20191215031303/https://github.com/t-d-k/LibreCrypt/blob/master/docs/plausible_deniability.md |date=2019-12-15 }})</ref> Offers an extensive range of encryption options, and doesn't need to be installed before use as long as the user has administrator rights.

*[[Off-the-Record Messaging]], a cryptographic technique providing true deniability for [[instant messaging]].

*[[OpenPuff]], freeware semi-open-source steganography for MS Windows.

*[[StegFS]], the current successor to the ideas embodied by the Rubberhose and PhoneBookFS filesystems.

*[[Vanish (computer science)|Vanish]], a research prototype implementation of self-destructing data storage.

*[[VeraCrypt]] (a successor to a discontinued [[TrueCrypt]]), an [[OTFE|on-the-fly disk encryption]] software for [[Windows]], [[MacOS|Mac]] and [[Linux]] providing limited deniable encryption<ref>{{Cite web |url=http://www.truecrypt.org/hiddenvolume.php |title=TrueCrypt - Free Open-Source On-The-Fly Disk Encryption Software for Windows Vista/XP, Mac OS X, and Linux - Hidden Volume<!-- Bot generated title --> |access-date=2006-02-16 |archive-date=2013-10-15 |archive-url=https://archive.today/20131015034241/http://www.truecrypt.org/hiddenvolume.php |url-status=live }}</ref> and to some extent (due to limitations on the number of hidden volumes which can be created<ref name="truecrypt.org" />) [[plausible deniability]], without needing to be installed before use as long as the user has full administrator rights.

===Detection===
The existence of hidden encrypted data may be revealed by flaws in the implementation.<ref>{{cite journal |author=Adal Chiriliuc |title=BestCrypt IV generation flaw |date=2003-10-23 |url=http://adal.chiriliuc.com/bc_iv_flaw.php |accessdate=2006-08-23 |archive-url=https://web.archive.org/web/20060721044156/http://adal.chiriliuc.com/bc_iv_flaw.php |archive-date=2006-07-21 |url-status=dead }}</ref>{{Self-published inline|date=March 2024|certain=y}} It may also be revealed by a so-called [[watermarking attack]] if an inappropriate cipher mode is used.<ref>[title=https://lists.gnu.org/archive/html/qemu-devel/2013-07/msg04229.html {{Webarchive|url=https://web.archive.org/web/20160702002846/https://lists.gnu.org/archive/html/qemu-devel/2013-07/msg04229.html |date=2016-07-02 }} [Qemu-devel] QCOW2 cryptography and secure key handling]</ref>
The existence of the data may be revealed by it 'leaking' into non-encrypted disk space<ref>{{Cite web |url=http://news.techworld.com/security/102171/encrypted-hard-drives-may-not-be-safe/ |title=Encrypted hard drives may not be safe: Researchers find that encryption is not all it claims to be. |access-date=2011-10-08 |archive-date=2013-03-30 |archive-url=https://web.archive.org/web/20130330154644/http://news.techworld.com/security/102171/encrypted-hard-drives-may-not-be-safe/ |url-status=dead }}</ref> where it can be detected by [[Computer forensics|forensic]] tools.<ref>http://www.forensicfocus.com/index.php?name=Forums&file=viewtopic&t=3970 {{Webarchive|url=https://web.archive.org/web/20140905190638/http://www.forensicfocus.com/index.php?name=Forums&file=viewtopic&t=3970 |date=2014-09-05 }} Is there any way to tell in Encase if there is a hidden truecrypt volume? If so how?</ref>{{Self-published inline|date=March 2024|certain=y}}

Doubts have been raised about the level of plausible deniability in 'hidden volumes'<ref>{{Cite web |url=https://gitlab.com/cryptsetup/cryptsetup/wikis/FrequentlyAskedQuestions#c17 |title=Plausible deniability support for LUKS |access-date=2015-07-03 |archive-date=2019-10-21 |archive-url=https://web.archive.org/web/20191021003129/https://gitlab.com/cryptsetup/cryptsetup/wikis/FrequentlyAskedQuestions#c17 |url-status=live }}</ref>{{Self-published inline|date=March 2024|certain=y}} &ndash; the contents of the "outer" container filesystem have to be 'frozen' in its initial state to prevent the user from corrupting the hidden volume (this can be detected from the access and modification timestamps), which could raise suspicion. This problem can be eliminated by instructing the system not to protect the hidden volume, although this could result in lost data.{{Cn|date=March 2024}}

===Drawbacks===
Possession of deniable encryption tools could lead attackers to continue torturing a user even after the user has revealed all their keys, because the attackers could not know whether the user had revealed their last key or not. However, knowledge of this fact can disincentivize users from revealing any keys to begin with, since they will never be able to prove to the attacker that they have revealed their last key.<ref>{{Cite web |url=http://embeddedsw.net/doc/physical_coercion.txt |title=Julian Assange: Physical Coercion |access-date=2011-10-08 |archive-date=2013-07-23 |archive-url=https://web.archive.org/web/20130723100802/http://embeddedsw.net/doc/physical_coercion.txt |url-status=live }}</ref>

==Deniable authentication==
{{No sources|section|date=March 2024}}
Some in-transit encrypted messaging suites, such as [[Off-the-Record Messaging]], offer [[deniable authentication]] which gives the participants [[plausible deniability]] of their conversations. While deniable authentication is not technically "deniable encryption" in that the encryption of the messages is not denied, its deniability refers to the inability of an adversary to prove that the participants had a conversation or said anything in particular.

This is achieved by the fact that all information necessary to forge messages is appended to the encrypted messages &ndash; if an adversary is able to create digitally authentic messages in a conversation (see [[hash-based message authentication code]] (HMAC)), they are also able to [[forgery|forge]] messages in the conversation. This is used in conjunction with [[perfect forward secrecy]] to assure that the compromise of encryption keys of individual messages does not compromise additional conversations or messages.

==See also==
*{{annotated link|Chaffing and winnowing}}
*{{annotated link|Deniable authentication}}
*{{annotated link|dm-crypt}}
*{{annotated link|Key disclosure law}}
*{{annotated link|Plausible deniability}}
*{{annotated link|Steganography}}
*{{annotated link|Unicity distance}}

==References==
{{Reflist|30em}}

==Further reading==
*{{cite conference |last=Czeskis |first=A. |author2=St. Hilaire, D. J. |author3=Koscher, K. |author4=Gribble, S. D. |author5=Kohno, T. |author6=Schneier, B.  |title=Defeating Encrypted and Deniable File Systems: TrueCrypt v5.1a and the Case of the Tattling OS and Applications |book-title=3rd Workshop on Hot Topics in Security |year=2008 |url=http://www.usenix.org/event/hotsec08/tech/full_papers/czeskis/czeskis.pdf |publisher=USENIX}}
*{{cite conference | last1=Howlader | first1=Jaydeep|last2=Basu|first2=Saikat|title=Sender-Side Public Key Deniable Encryption Scheme|book-title=Proceedings of the International Conference on Advances in Recent Technologies in Communication and Computing|year = 2009|publisher=IEEE|doi=10.1109/ARTCom.2009.107}}
*{{cite conference | last1=Howlader | first1=Jaydeep|last2=Nair|first2=Vivek|last3=Basu|first3=Saikat|title=Deniable Encryption in Replacement of Untappable Channel to Prevent Coercion|book-title=Proc. Advances in Networks and Communications|year = 2011|series= Communications in Computer and Information Science |volume=132|pages= 491–501 |publisher=Springer|doi=10.1007/978-3-642-17878-8_50}}

{{DEFAULTSORT:Deniable Encryption}}
[[Category:Cryptography]]