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. Deniable authentication 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 – 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 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. Software OpenPuff, freeware semi-open-source steganography for MS Windows. LibreCrypt, opensource transparent disk encryption for MS Windows and PocketPC PDAs that provides both deniable encryption and plausible deniability. 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. Rubberhose, defunct project (last release in 2000, not compatible with modern Linux distributions) StegFS, the current successor to the ideas embodied by the Rubberhose and PhoneBookFS filesystems. VeraCrypt (a successor to a discontinued TrueCrypt), an on-the-fly disk encryption software for Windows, Mac and Linux providing limited deniable encryption and to some extent (due to limitations on the number of hidden volumes which can be created)plausible deniability, without needing to be installed before use as long as the user has full administrator rights. Vanish, a research prototype implementation of self-destructing data storage. See also References Further reading Cryptography