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 adve ...
, a zero-knowledge password proof (ZKPP) is a type of
zero-knowledge proof that allows one party (the prover) to prove to another party (the verifier) that it knows a value of a
password
A password, sometimes called a passcode (for example in Apple devices), is secret data, typically a string of characters, usually used to confirm a user's identity. Traditionally, passwords were expected to be memorized, but the large number of ...
, without revealing anything other than the fact that it knows the password to the verifier. The term is defined in
IEEE P1363.2, in reference to one of the benefits of using a
password-authenticated key exchange (PAKE) protocol that is secure against off-line dictionary attacks. A ZKPP prevents any party from verifying guesses for the password without interacting with a party that knows it and, in the optimal case, provides exactly one guess in each interaction.
A common use of a zero-knowledge password proof is in
authentication
Authentication (from ''authentikos'', "real, genuine", from αὐθέντης ''authentes'', "author") is the act of proving an assertion, such as the identity of a computer system user. In contrast with identification, the act of indicati ...
systems where one party wants to prove its identity to a second party using a password but doesn't want the second party or anybody else to learn anything about the password. For example, apps can validate a password without processing it and a payment app can check the balance of an account without touching or learning anything about the amount.
History
The first methods to demonstrate a ZKPP were the
encrypted key exchange methods (EKE) described by
Steven M. Bellovin
Steven M. Bellovin is a researcher on computer networking and security. He has been a professor in the Computer Science department at Columbia University since 2005. Previously, Bellovin was a Fellow at AT&T Labs Research in Florham Park, New Jers ...
and Michael Merritt in 1992. A considerable number of refinements, alternatives, and variations in the growing class of password-authenticated key agreement methods were developed in subsequent years. Standards for these methods include IETF ,
IEEE P1363.2, and ISO-IEC 11770-4.
See also
*
Cryptographic protocol
*
Outline of cryptography
*
Key-agreement protocol In cryptography, a key-agreement protocol is a protocol whereby two or more parties can agree on a key in such a way that both influence the outcome. If properly done, this precludes undesired third parties from forcing a key choice on the agreeing ...
*
Secure Remote Password protocol
References
External links
David Jablon's links for password-based cryptography
{{crypto-stub
Password authentication