In
cryptography
Cryptography, or cryptology (from grc, , translit=kryptós "hidden, secret"; and ''graphein'', "to write", or ''-logia'', "study", respectively), is the practice and study of techniques for secure communication in the presence of adver ...
, deniable authentication refers to
message authentication
In information security, message authentication or data origin authentication is a property that a message has not been modified while in transit (data integrity) and that the receiving party can verify the source of the message. Message authentica ...
between a set of participants where the participants themselves can be confident in the authenticity of the messages, but it cannot be proved to a third party after the event.
In practice, deniable authentication between two parties can be achieved through the use of
message authentication code
In cryptography, a message authentication code (MAC), sometimes known as a ''tag'', is a short piece of information used for authenticating a message. In other words, to confirm that the message came from the stated sender (its authenticity) and ...
s (MACs) by making sure that if an attacker is able to decrypt the messages, they would also know the MAC key as part of the protocol, and would thus be able to forge authentic-looking messages.
For example, in the
Off-the-Record Messaging (OTR) protocol, MAC keys are derived from the asymmetric decryption key through a
cryptographic hash function
A cryptographic hash function (CHF) is a hash algorithm (a map of an arbitrary binary string to a binary string with fixed size of n bits) that has special properties desirable for cryptography:
* the probability of a particular n-bit output re ...
. In addition to that, the OTR protocol also reveals used MAC keys as part of the next message, after they have already been used to authenticate previously received messages, and will not be re-used.
See also
*
Deniable encryption
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.
The users ...
*
Plausible deniability
Plausible deniability is the ability of people, typically senior officials in a formal or informal chain of command, to denial, deny knowledge of or responsibility for any damnable actions committed by members of their organizational hierarchy. Th ...
*
Malleability
Ductility is a List of materials properties, mechanical property commonly described as a material's amenability to Drawing (manufacturing), drawing (e.g. into wire). In materials science, ductility is defined by the degree to which a materia ...
*
Undeniable signature An undeniable signature is a digital signature scheme which allows the signer to be selective to whom they allow to verify signatures. The scheme adds explicit signature repudiation, preventing a signer later refusing to verify a signature by omissi ...
References
Cryptographic protocols
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