Why do passkeys not eliminate the need for continuous authentication?

Passkeys reduce phishing and credential replay, but they only prove the user at the point of login. They do not prove the same user is still present after session hijack, device compromise, or account takeover. Continuous authentication addresses that gap by reassessing trust during the session, not just at entry.

Why This Matters for Security Teams

Passkeys materially improve authentication by removing shared secrets and reducing phishing exposure, but they do not convert a one-time sign-in into a continuously trusted session. That distinction matters because modern attacks often succeed after the login event, through token theft, device malware, remote access abuse, or browser session hijacking. Security teams that treat passkeys as a complete substitute for ongoing verification often leave the session layer underprotected.

This is why continuous authentication remains relevant alongside passkeys. It gives defenders a way to reassess trust based on signals such as device posture, location shifts, behavioural anomalies, and session integrity. The control objective aligns with broader identity and access governance in NIST SP 800-53 Rev 5 Security and Privacy Controls, especially where organisations need stronger assurance around session management and access enforcement. Passkeys lower one class of risk, but they do not solve post-authentication compromise.

In practice, many security teams encounter account abuse only after a valid session has already been established, rather than through intentional authentication failure.

How It Works in Practice

Continuous authentication works by making trust conditional instead of static. After the initial passkey ceremony, the system keeps evaluating whether the current session still looks legitimate. That can include device health checks, IP or geolocation change, behavioural signals, reauthentication prompts for sensitive actions, and session binding to a trusted browser or device state. The key point is that passkeys prove possession of a credential at login, while continuous authentication checks whether the risk picture has changed during the session.

In mature environments, this is usually implemented as part of a broader access policy rather than a standalone product feature. The policy engine decides when to step up verification, revoke or shorten a session, or require a new authenticator. Good practice is to use continuous signals sparingly and with clear thresholds, because overuse creates friction and can train users to ignore prompts. For governance, many teams map these controls to identity assurance and access management requirements in ISO/IEC 27001:2022 Information Security Management, especially where session control supports formal risk treatment.

• Use passkeys for strong initial authentication and phishing resistance.
• Add risk-based checks for session drift, device compromise, and anomalous behaviour.
• Require step-up verification for sensitive transactions or privilege changes.
• Set short-lived sessions where risk is high and revocation is operationally feasible.

Continuous authentication is most effective when tied to identity lifecycle, device trust, and detection tooling, not just the login flow. These controls tend to break down in unmanaged-device environments because the organisation cannot reliably measure device posture or session integrity.

Common Variations and Edge Cases

Tighter session verification often increases user friction and support overhead, requiring organisations to balance stronger assurance against usability and business continuity. That tradeoff becomes more visible in customer-facing environments, remote work scenarios, and high-change operating conditions where legitimate behaviour can look suspicious.

There is no universal standard for how often a session should be re-evaluated yet. Current guidance suggests using continuous authentication as a risk-adaptive layer, not as a fixed timer that forces re-login on every interval. Some environments rely on silent background signals, while others only step up when a transaction is sensitive or the risk score changes materially. The right model depends on whether the priority is workforce access, privileged access, or high-value customer transactions.

Passkeys also do not eliminate the need for session protections such as token binding, secure cookie handling, device revocation, and anomaly detection. If a browser session is stolen after login, the passkey itself is not the weak point. The weak point is the ongoing trust boundary. That is why continuous authentication should be treated as part of a layered session security design, not as an alternative to modern authentication methods.

For regulated or high-assurance programmes, continuous authentication is strongest when paired with documented policies for access review, incident response, and session termination, using controls that are auditable and consistently enforced.

Related resources from NHI Mgmt Group

• How do continuous authentication and passkeys fit together in IAM programmes?
• What is the difference between initial authentication and continuous authorization?
• What is the difference between MFA protection and continuous authentication?
• What is the difference between MFA and continuous authentication in zero trust?