FIDO-CTAP specification is part of the FIDO2 project which includes this CTAP and the FIDO Server Guidelines specifications, and is related to the W3C WebAuthN specification.

FIDO-CTAP specification refers to two CTAP protocol versions:

  • CTAP1 or U2F protocol, which is defined by the U2F Raw Messages specification [U2FRawMsgs]. CTAP1/U2F messages are recognizable by their APDU-like binary structure. CTAP1/U2F may also be referred to as CTAP 1.2 or U2F 1.2. The latter was the U2F specification version used as the basis for several portions of this specification. Authenticators implementing CTAP1/U2F are typically referred to as U2F authenticators or CTAP1 authenticators.

Both CTAP1 and CTAP2 share the same underlying transports: USB Human Interface Device (USB HID), Near Field Communication (NFC), and Bluetooth Smart / Bluetooth Low Energy Technology (BLE).

The [U2FUsbHid], [U2FNfc], [U2FBle], and [U2FRawMsgs] specifications, specifically, are superseded by this specification.

Occasionally, the term "CTAP" may be used without clarifying whether it is referring to CTAP1 or CTAP2. In such cases, it should be understood to be referring to the entirety of this specification or portions of this specification that are not specific to either CTAP1 or CTAP2. For example, some error messages begin with the term "CTAP" without clarifying whether they are CTAP1- or CTAP2-specific because they are applicable to both CTAP protocol versions. CTAP protocol-specific error messages are prefixed with either "CTAP1" or "CTAP2" as appropriate.

FIDO Alliance Metadata Service#

The FIDO Alliance Metadata Service (MDS) is a web-based tool where FIDO authenticator vendors can publish metadata statements for FIDO servers to download. This provides organizations deploying FIDO servers with a centralized and trusted source of information about FIDO authenticators.

More Information#

There might be more information for this subject on one of the following: