YubiKey, Duo, RSA or passkey? Choose the right hardware token

Ranked for your requirements

Phishing resistance follows NIST SP 800-63B-4 and CISA; the fit points are PlayCISO's weights, all shown. Most organisations end up with a mix: the top option for most people, another for specific gaps.

1. 1

   FIDO2 security keys

   Best fitPhishing-resistant

   Examples: YubiKey 5 and Security Key series, Feitian, Google Titan, RSA iShield Key 2, Token2 and other FIDO2-certified keys. Check vendor pricing.

   • + Phishing-resistant and device-bound, the strongest general-purpose option.
   • + You want strong protection against phishing.
   • + Some apps accept FIDO2; start with those and the IdP.
   • + Privileged accounts need a non-exportable key; hardware keys are the usual answer for admins.
   • + Multi-protocol models (YubiKey 5, iShield Key 2) also do OTP for the legacy apps.

   NIST / CISA position, pros and cons

   Phishing-resistant: WebAuthn binds the sign-in to the real site name (verifier name binding), so a look-alike site gets nothing it can replay. CISA lists FIDO/WebAuthn as phishing-resistant.

   Assurance level: Device-bound, non-exportable key: can meet AAL3 when the key is FIPS 140-validated (for example YubiKey 5 FIPS or RSA iShield Key 2) and the verifier meets the rest of AAL3.

   Pros: Strongest phishing resistance for everyday use; Roams between machines, so it works on shared workstations; No phone, battery or network needed on the key; Many models also do PIV smart card and OTP for legacy apps.

   Cons: Per-user hardware cost and logistics; plan two keys per person for backup; Every app must accept FIDO2/WebAuthn, directly or through SSO; Lost-key recovery must not fall back to something phishable.

   Source: NIST, CISA, Yubico, Yubico, Google, RSA

2. 2

   Platform passkeys and Windows Hello for Business

   For specific gapsPhishing-resistant

   Examples: Synced passkeys (Apple iCloud Keychain, Google Password Manager), device-bound passkeys (Windows Hello for Business, passkeys in Microsoft Authenticator). Check vendor pricing.

   • + Phishing-resistant with no extra hardware.
   • + Strong protection against phishing at low cost.

   NIST / CISA position, pros and cons

   Phishing-resistant: passkeys use WebAuthn, the same origin binding as security keys.

   Assurance level: Synced passkeys are fine at AAL2 but NIST says syncable authenticators SHALL NOT be used at AAL3. Device-bound platform keys can meet the non-exportable requirement.

   Pros: No extra hardware: uses the laptop or phone people already have; Fast sign-in with a fingerprint, face or PIN; Easy to roll out to large numbers through your IdP.

   Cons: Tied to one device or one platform account: poor for shared workstations; Synced passkeys are not AAL3 and their security depends on the sync account; Recovery depends on the device or the cloud account.

   Source: NIST, CISA, Microsoft

3. 3

   Authenticator apps (push with number matching, or TOTP)

   Poor fitNot phishing-resistant

   Examples: Microsoft Authenticator, Duo Mobile, Okta Verify, Google Authenticator and other TOTP apps. Check vendor pricing.

   • + Quick, low-cost MFA for everyone with a phone.
   • + Personal phones are allowed.
   • + TOTP codes cover OTP-only systems.
   • − Phishable by real-time relay; use number matching at minimum.

   NIST / CISA position, pros and cons

   Not phishing-resistant: CISA lists app-based OTP and push with number matching as vulnerable to phishing (number matching does stop push bombing). Some of these apps can also hold passkeys, which are phishing-resistant.

   Assurance level: AAL2 with a password; not AAL3.

   Pros: Lowest cost: no hardware to buy; Fast to roll out to everyone with a phone; CISA's recommended interim step for organisations that cannot go phishing-resistant yet.

   Cons: Phishable by real-time relay; Needs a phone for every user, which rules out some roles; Push without number matching invites MFA fatigue attacks.

   Source: CISA, NIST

4. 4

   Smart cards / PIV (certificate-based)

   Poor fitPhishing-resistant

   Examples: PIV and CAC cards, YubiKey 5 PIV, RSA iShield Key 2 smart card, with certificate-based authentication in your IdP or Active Directory. Check vendor pricing.

   • + Phishing-resistant through certificate-based authentication.

   NIST / CISA position, pros and cons

   Phishing-resistant: certificate-based client-authenticated TLS is NIST's example of channel binding, and CISA lists PKI-based MFA as phishing-resistant.

   Assurance level: Hardware-held, non-exportable key: AAL3-capable with FIPS-validated cards or tokens.

   Pros: Works with on-prem Active Directory and Windows logon with no cloud dependency, so it suits air-gapped sites; The standard for US federal staff (PIV); One card can also be the building badge.

   Cons: Needs a PKI: certificate authority, issuance, renewal and revocation; Card readers or USB tokens on every machine; More admin effort than FIDO2 for small teams.

   Source: NIST, CISA, OMB, Yubico

5. 5

   Hardware OTP tokens

   Poor fitNot phishing-resistant

   Examples: Duo D-100 (HOTP, one code per button press), RSA SecurID hardware tokens such as the SID700 key fob, OATH TOTP tokens from vendors such as Token2 and Feitian. Check vendor pricing.

   • + Codes work almost anywhere a code box exists.
   • + A few OTP-only systems need covering.
   • − OTP codes can be phished and relayed.

   NIST / CISA position, pros and cons

   Not phishing-resistant: NIST says "OTP authentication is not phishing-resistant", and CISA lists token-based OTP as vulnerable to phishing, because a fake site can relay the code in real time.

   Assurance level: Can reach AAL2 combined with a password; not AAL3.

   Pros: Works with legacy apps, VPNs and RADIUS that only accept a code; No phone needed, and the token itself needs no network; Simple for users who cannot or will not use a phone.

   Cons: Codes can be phished and relayed by adversary-in-the-middle kits; Batteries and seed files to manage; check which code type your IdP accepts (Entra ID accepts TOTP but not HOTP); Vendor-specific tokens may only work with that vendor's platform.

   Source: NIST, CISA, Cisco Duo, RSA, Microsoft