Passkeys and FIDO2 in Microsoft Entra ID

Passkeys and FIDO2 security keys are the only Entra ID authentication methods that are genuinely phishing-resistant. This skill covers a pragmatic rollout: pick the right passkey types for your population, bootstrap via Temporary Access Pass, enforce via Conditional Access authentication strength, then retire legacy methods.

When to use

Moving an Entra tenant from password+SMS/app-push toward passwordless, phishing-resistant authentication. Use for method selection, registration campaigns, CA enforcement, and legacy-method retirement planning.

Do not use this skill for generic CA policy authoring (conditional-access-mfa), full Windows Hello for Business desktop design (windows-hello), or Verified ID credential issuance (entra-verified-id).

Passkey types — pick per population

Rule of thumb: Default population = device-bound Authenticator passkey. Admins and tier-0 = hardware key. Mac/iPhone users where MDM/policy permits = synced passkey from the OS keychain.

Approach

1. Enable the authentication methods. In Entra → Authentication methods, enable:
   • Passkey (FIDO2) with explicit attestation enforcement decisions (see below).
   • Microsoft Authenticator including passkey capability.
   • Temporary Access Pass. Scope rollout to a pilot group first.
2. Attestation policy. Decide whether to require attestation for FIDO2 registrations:
   • Enforce attestation = Yes: only AAGUIDs (authenticator models) you allowlist can register. Strong control; logistics-heavy because new device models need allowlisting.
   • Enforce attestation = No: any FIDO2 authenticator (incl. synced passkeys from platform providers) can register. Lower friction; less control. For privileged populations: enforce + allowlist hardware keys. For workforce: permissive.
3. Bootstrap with Temporary Access Pass. Every user needs a way to register their first passkey without using a password. TAP gives a time-bound, single-use (or limited-use) code:
   • New hires: TAP issued by HR/onboarding flow.
   • Existing users in registration campaign: TAP issued by help desk on verification.
   • Lost-device recovery: re-issue TAP after identity proofing (consider Verified ID).
4. Registration campaign. Use the built-in registration campaign to nudge users to set up Authenticator passkeys at sign-in. Run for 60–90 days; measure adoption. Pair with comms: 3 emails + a Teams banner.
5. Conditional Access — authentication strength. Create a CA policy requiring Phishing-resistant MFA authentication strength for:
   • All admin roles (Global Admin, Privileged Role Admin, etc.).
   • Privileged applications (Azure portal, Entra admin center, Exchange admin, GitHub Enterprise sign-in).
   • High-impact data apps (SAP, HR, finance). Roll out per-app, not tenant-wide, to limit blast radius.
6. Retire weak methods.
   • SMS and voice — disable as MFA methods in Authentication methods policy. They remain available for SSPR only if you must.
   • Authenticator push without number-matching — number-matching is now default; confirm enforced.
   • Legacy MFA registration page — move to combined registration (long since default). Sequence: weaken first (mark "secondary"), monitor sign-in logs for users still relying on the method, then disable.
7. Lifecycle.
   • Lost device: revoke the registered authenticator in user's authentication methods, issue new TAP, user re-registers.
   • Job change: passkey persists — it's bound to the user identity. Re-evaluation of CA strength happens on next sign-in.
   • Termination: standard offboarding revokes the identity; passkey becomes useless.
8. Reporting. In Entra → Monitoring → Authentication methods activity, track:
   • % users with at least one phishing-resistant method registered.
   • % sign-ins using phishing-resistant methods.
   • Method usage by application. Target: 100% of admins on phishing-resistant within 60 days; 90% of workforce within 12 months.

Guardrails

• Don't enforce phishing-resistant CA before registration coverage is high enough. Lockouts at 9 a.m. Monday. Phase: registration campaign first, then enforcement per group.
• TAP must be issued by an identity-verified channel (help desk with strong verification, Verified ID, in-person). A leaked TAP is a passwordless bypass.
• Synced passkeys cross device trust boundaries. A user signing in from a personal Mac uses the same passkey as their corporate Mac. If that's not your threat model, use device-bound passkeys or hardware keys for the sensitive personas.
• Attestation allowlist requires lifecycle management. New YubiKey model = new AAGUID. Bake into procurement.
• Number-matching MFA is not phishing-resistant. It defeats MFA-fatigue spam but a real-time AiTM proxy still succeeds. Don't conflate them.
• SMS as a fallback "just in case" defeats the program. Attackers will target the fallback. Remove it for the populations under phishing-resistant CA.
• Don't ship Conditional Access "authentication strength: phishing-resistant" with break-glass accounts in scope. Always exclude break-glass.

Common anti-patterns

• "Mandatory passkeys for admins on day one with no registration campaign" — admins locked out at the worst moment.
• "SMS allowed as MFA backup for everyone, forever" — SIM-swap and lure attacks hit the weakest method. Remove for tier-0 day one.
• "TAP issued via email to user's mailbox they can't access without MFA" — chicken-and-egg. Use help-desk channel with identity proofing.
• "Attestation enforced + brand-new YubiKey model not allowlisted" — procurement-day surprise. Maintain the allowlist.
• "Synced passkeys for Global Admins on personal iCloud" — admin credential on a personal phone. Use hardware key + device-bound for admins.
• "Number-matching MFA called phishing-resistant" — it isn't. AiTM defeats it.
• "Disabled password sign-in tenant-wide before workforce coverage hit 95%" — unregistered users locked out. Use CA per-app + monitor first.

Example prompts

• Plan a 12-month passkey rollout for 25,000 users: pilot, campaign, CA enforcement, legacy retirement.
• Issue hardware FIDO2 keys to 300 admins with attestation enforced; build the AAGUID allowlist.
• Author a Conditional Access policy requiring phishing-resistant MFA for Global Administrators and the Azure portal.
• Replace SMS MFA with Authenticator passkey for a regulated population in 90 days.
• Bootstrap new hires with a Temporary Access Pass via the HR onboarding flow.
• Build a passkey registration campaign with success metrics and rollback plan.
• Recover a user who lost their phone and their only FIDO2 key — runbook with identity verification.
• Compare device-bound vs synced passkeys for a Mac-heavy creative workforce.

Microsoft Learn

• Passkey overview in Entra: https://learn.microsoft.com/entra/identity/authentication/concept-authentication-passkeys-fido2
• Microsoft Authenticator passkeys: https://learn.microsoft.com/entra/identity/authentication/how-to-enable-authenticator-passkey
• FIDO2 security keys: https://learn.microsoft.com/entra/identity/authentication/concept-authentication-passkeys-fido2
• Attestation and AAGUIDs: https://learn.microsoft.com/entra/identity/authentication/concept-fido2-compatibility
• Temporary Access Pass: https://learn.microsoft.com/entra/identity/authentication/howto-authentication-temporary-access-pass
• Authentication strengths in CA: https://learn.microsoft.com/entra/identity/authentication/concept-authentication-strengths
• Registration campaign: https://learn.microsoft.com/entra/identity/authentication/how-to-mfa-registration-campaign
• Number-matching MFA: https://learn.microsoft.com/entra/identity/authentication/how-to-mfa-number-match
• Retire SMS/voice: https://learn.microsoft.com/entra/identity/authentication/how-to-authentication-methods-manage