What Is Ctap

Client-to-Authenticator Protocol (commonly referred to as CTAP) is a protocol developed by the FIDO Alliance that enables a client device to communicate with an device that is designed to authenticate the user. For example, CTAP could be responsible for controlling the communication between a USB key and an authentication token. In such context, CTAP’s function is to ensure a secure communication between two parties, so that the authentication and login process can happen as smoothly as possible.

CTAP is often an important component of passwordless authentication, which is a more secure and convenient alternative to the password-based authentication systems we all know. FIDO2 and WebAuthn are examples of systems designed to replace password-based authentication.

There are currently two versions of CTAP that are available:

• CTAP1 (or FIDO U2F protocol), which is used with older security keys and devices
• CTAP2, which integrates more modern authentication methods such as biometrics

An increasing number of browsers, security devices, and operating systems now support CTAP. However, it’s important to note that it’s not only the client device that needs to support this protocol, but also the authentication device. Only once both devices support CTAP, it’s possible to proceed.