HardwareTokens

Hardware tokens are physical devices used to authenticate a user to a digital service. They come in several form factors, including small key fobs that generate one-time passwords, USB or NFC security keys, and smart cards. They are designed to work without relying on a mobile device or trusted software tokens.

Common types include time-based one-time password (TOTP) tokens, which display a numeric code that changes every 30–60 seconds, and event-based HOTP tokens, which produce a code after a button press. USB security keys that support FIDO U2F or FIDO2/WebAuthn provide cryptographic credentials for online services and can optionally support PKI smart-card formats.

In OTP tokens, a shared secret is stored on both token and server; the server validates the code. In FIDO-based tokens, the device holds a private key and performs a signature with a public key registered at the service; authentication is often phishing-resistant and may require user interaction (touch).

Use cases: enterprise authentication for VPNs and corporate portals, access to cloud services, email, and network devices. Some tokens also support offline verification and do not require network connectivity; others rely on an online backend.

Advantages and limitations: Hardware tokens can be more resistant to malware and phishing (especially FIDO2/WebAuthn) and do not depend on a mobile device or SMS. However, they incur cost, require management, and can be lost or damaged; provision, rotation, and revocation add administrative overhead.

Security considerations: tokens should be tamper-resistant, firmware updated, and revocation lists maintained. Loss should trigger credential disablement and a backup factor. Users should be trained to recognize tamper attempts and to avoid sharing codes.

Standards include HOTP/TOTP (RFC 4226/6238), FIDO U2F (FIDO Alliance), FIDO2/WebAuthn, PKI smart cards (PIV, CAC).