What Is Passwordless Authentication?
Passwordless authentication replaces the traditional username and password with cryptographic credentials tied to a device or biometric. Users verify their identity the same way they unlock their phone: a fingerprint, face scan, PIN, or hardware security key. No password is created, transmitted, or stored.
The underlying standard is FIDO2, developed by the FIDO Alliance and supported natively across Windows, macOS, iOS, Android, and every major browser. Passkeys, Windows Hello for Business, and hardware security keys are all built on FIDO2. When implemented correctly, passwordless authentication is both more secure and easier to use than traditional passwords combined with MFA.
Why Passwords Are the Problem
Credential-based attacks account for the majority of data breaches. Passwords can be phished, stolen from breach databases, guessed, and reused across accounts. Even strong passwords with MFA have been bypassed through social engineering and SIM swapping.
Passwordless authentication removes the shared secret entirely. There's no password to steal, no phishing page that can capture it, and no credential database to breach. The private key never leaves the user's device. A fake login page can't complete authentication because it can't satisfy the cryptographic challenge tied to the legitimate service.
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Passwordless Methods
Passwordless authentication isn't one thing. Several methods exist, each with different security levels and use cases. STACK helps you select and implement the right combination for your environment.
Passkeys
FIDO2 credentials synced across a user's trusted devices via their platform provider. Users authenticate with a biometric or device PIN, with no password involved at any point.
Windows Hello for Business
Device-bound FIDO2 credentials for Windows workstations, using biometrics or PIN secured by the device's Trusted Platform Module. Integrates natively with Microsoft Entra ID and Intune.
Hardware Security Keys
Physical FIDO2 keys (such as YubiKey) provide the highest level of phishing resistance. Recommended for privileged accounts, administrators, and environments with elevated compliance requirements.
Microsoft Authenticator Passkey
Passkeys stored in the Microsoft Authenticator app on a registered mobile device provide passwordless access to Microsoft 365 and Entra ID resources with biometric or PIN verification.
Phishing-Resistant MFA
For environments not yet ready for full passwordless, FIDO2 can be layered as a second factor alongside existing credentials, delivering phishing resistance without a complete credential overhaul.
Compliance Alignment
NIST SP 800-63B and CMMC both recognize phishing-resistant authentication as the highest assurance level. Hardware security keys and passkeys satisfy these requirements out of the box.
How It Works
When a user registers a passkey or security key with a service, a unique cryptographic key pair is generated. The private key stays on the user's device, secured by hardware. The public key is registered with the service.
When the user authenticates, the service sends a cryptographic challenge. The user's device signs it with the private key after verifying the user's identity locally through a biometric or PIN. The service validates the signature using the stored public key. The private key never leaves the device, and no shared secret is ever transmitted. A phishing page can't capture what's never sent.
Rolling It Out Without Disruption
Passwordless doesn't have to be an all-or-nothing transition. Most businesses start where credential risk is highest: privileged accounts, remote access, and cloud application logins. STACK manages a phased rollout that moves high-risk users first, gathers feedback, and expands from there.
Environment Assessment
We identify which applications, accounts, and access points are ready for passwordless and where phased implementation makes the most sense.
Configuration
Identity provider policies, Intune device enrollment, and application registrations are configured to support FIDO2 and passkey authentication.
User Enrollment
Employees are guided through registering their passkeys or security keys, with clear instructions and support to minimize friction during the transition.
Lifecycle Management
Lost keys and device changes are handled through defined recovery procedures. Access is updated as employees onboard, offboard, or change roles.
Ready to Move Beyond Passwords?
You don't have to eliminate passwords overnight. STACK can assess where credential risk is highest in your environment and implement phishing-resistant authentication where it matters most, with a roadmap for broader rollout over time.