Yubico Security Key C NFC review

The Security Key C NFC is Yubico's FIDO-focused key with a USB-C plug and NFC. It supports FIDO2 CTAP 2.1 and FIDO U2F. Yubico lists no PIV, OpenPGP, OATH or Yubico OTP. That makes it a sign-in key for services that accept passkeys or security-key two-factor, and little else.

The USB-A version is a separate product, Security Key NFC by Yubico. This page covers the USB-C model only.

This key supports both FIDO2 and U2F. If you want smart card login through PIV, OpenPGP signing, or one-time codes from the key itself, the listed specifications rule those out. A sysadmin who wants a single key for SSH, code signing and web logins will find the protocol list too short. Someone who only needs strong account protection will find it covers the job.

The key has a USB-C 2.0 connector and NFC. There is no USB-A. With both a wired and a tap option, it can connect to a laptop with a USB-C port or to a phone that reads NFC. A machine with only USB-A ports is outside what this model offers, and Yubico sells the USB-A version separately.

The key stores up to 100 discoverable credentials on firmware 5.7 or later. On firmware 5.0 to 5.6 the limit is 25. Non-discoverable credentials are unlimited. The firmware listed for this model is 5.8, which falls in the 100-credential range. With that ceiling, a person with a long list of accounts that use passkeys has room before the key fills up.

The key is FIDO2 L2 certified. It is not FIPS 140-2 certified. Buyers whose employer or contract requires FIPS validation should treat that as a clear gap. The listed firmware version is 5.8. The specifications don't state whether the firmware can be updated, or what Yubico's advisory record looks like for this model. Check Yubico's own security advisories before you rely on it in a regulated setting.

Yubico rates the key IP68 and crush resistant up to 25 N·m. It has no batteries and no moving parts, so there is nothing to charge or wear out mechanically. The operating temperature range is 0°C to 40°C. That covers normal indoor use, but a key left in a freezing vehicle would fall outside it.

A tray of 50 is also sold. The research found no price for the tray.

The three feedback themes in the research are all praise. People praise easy setup on desktop. They also report that it works across desktop operating systems and services. A third theme is that the key is small and portable. The research records no recurring complaints.

This is a FIDO2 and U2F key that holds up to 100 discoverable credentials on firmware 5.7 or later, with USB-C and NFC and a sealed, battery-free body. Those specifications suit personal accounts and work logins that accept security keys. The missing PIV, OpenPGP, OATH and OTP support, and the lack of FIPS certification, limit it for anyone with more specialised needs. For those buyers the protocol and certification lines above decide the matter.