The Client to Authenticator Protocol (CTAP) or X.1278
enables a roaming, user-controlled
cryptographic
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 ...
authenticator (such as a
smartphone
A smartphone is a portable computer device that combines mobile telephone and computing functions into one unit. They are distinguished from feature phones by their stronger hardware capabilities and extensive mobile operating systems, whic ...
or a hardware
security key
A security token is a peripheral device used to gain access to an electronically restricted resource. The token is used in addition to or in place of a password. It acts like an electronic key to access something. Examples of security tokens incl ...
) to interoperate with a
client
Client(s) or The Client may refer to:
* Client (business)
* Client (computing), hardware or software that accesses a remote service on another computer
* Customer or client, a recipient of goods or services in return for monetary or other valuabl ...
platform such as a
laptop.
Standard
CTAP is complementary to the Web Authentication (
WebAuthn) standard published by the
World Wide Web Consortium
The World Wide Web Consortium (W3C) is the main international standards organization for the World Wide Web. Founded in 1994 and led by Tim Berners-Lee, the consortium is made up of member organizations that maintain full-time staff working t ...
(W3C).
WebAuthn and CTAP are the primary outputs of the
FIDO2 Project, a joint effort between the
FIDO Alliance and the
W3C.
CTAP is based upon previous work done by the FIDO Alliance, in particular the
Universal 2nd Factor (U2F) authentication standard. Specifically, the FIDO U2F 1.2 Proposed Standard (July 11, 2017) became the starting point for the CTAP Proposed Standard, the latest version of which was published on January 30, 2019.
The CTAP specification refers to two protocol versions, the CTAP1/U2F protocol and the CTAP2 protocol.
An authenticator that implements CTAP2 is called a FIDO2 authenticator (also called a WebAuthn authenticator). If that authenticator implements CTAP1/U2F as well, it is backward compatible with U2F.
The protocol uses the
CBOR binary data serialization format.
The standard was adopted as
ITU-T
The ITU Telecommunication Standardization Sector (ITU-T) is one of the three sectors (divisions or units) of the International Telecommunication Union (ITU). It is responsible for coordinating standards for telecommunications and Information Commu ...
Recommendation X.1278.
References
{{Reflist
External links
FIDO Specifications OverviewFIDO Specifications
Authentication
Identification
Internet security
ITU-T recommendations
ITU-T X Series Recommendations