What is the difference between biometric authentication and one-time passwords in financial services?

Why This Matters for Security Teams

In financial services, the difference between biometric authentication and one-time passwords is not just a user experience question. It affects fraud resistance, account recovery, step-up authentication, and how much trust can be placed in the channel being used. Biometrics bind access to a person’s characteristics, while one-time passwords bind access to possession of a device or mailbox. That distinction matters when attackers are targeting SIM swaps, phishing kits, session hijacking, and social engineering.

For banks, insurers, payment providers, and fintech platforms, the real decision is not which method is “stronger” in the abstract, but which control best fits the transaction risk, regulatory expectations, and recovery path. Current guidance on identity assurance is clearer about verification and authentication outcomes than about any single method being universally superior, which is why programs often combine factors rather than rely on one. NIST SP 800-63 Digital Identity Guidelines is useful here because it separates authenticator strength from identity proofing and lifecycle management, and NIST SP 800-53 Rev 5 Security and Privacy Controls helps map those choices to broader access control and incident response requirements.

In practice, many security teams discover the weakness of a second factor only after account takeover has already started through the recovery channel, not through the login screen itself.

How It Works in Practice

Biometric authentication usually works as a local match between a captured trait and a stored template, often inside a device secure enclave or trusted hardware module. In financial services, that can support step-up login, mobile app access, payment approval, or call-centre verification. One-time passwords, by contrast, are typically delivered through SMS, email, voice, or an authenticator app and expire quickly after use. They are most useful as a possession factor, but their strength depends heavily on the security of the delivery path and the resistance of the surrounding workflow to phishing and interception.

Operationally, teams should treat both methods as part of a layered authentication design rather than a standalone answer. Key considerations include:

• Where the biometric template is stored and whether it can be replayed or exfiltrated.
• Whether the one-time password is delivered through a channel exposed to SIM swap, mailbox compromise, or session takeover.
• How the method behaves during device replacement, customer support reset, and high-risk transaction approval.
• Whether the authentication choice is tied to risk scoring, transaction context, or step-up policy.

For regulated environments, ISO/IEC 27001:2022 Information Security Management is relevant because authentication is only one part of a broader access governance system. Financial firms also need to consider whether the method supports auditability, privacy expectations, and fallback controls when a legitimate user cannot present the primary factor. These controls tend to break down when customer recovery flows are outsourced or poorly instrumented because attackers then target the weakest administrative path rather than the primary login flow.

Common Variations and Edge Cases

Tighter authentication often increases enrolment friction and support overhead, requiring organisations to balance fraud reduction against customer drop-off and recovery complexity. That tradeoff is especially visible in financial services, where accessibility, device diversity, and cross-border customer bases complicate one-size-fits-all deployment.

There is no universal standard for this yet on the question of whether biometrics should replace one-time passwords or simply complement them. Best practice is evolving toward risk-based authentication, where biometrics may be preferred for convenience and phishing resistance, while one-time passwords remain useful for fallback, transaction confirmation, or cases where biometric capture is not feasible. However, biometrics create their own governance issues: unlike a code, a biometric trait cannot be rotated if compromised, so enrolment quality, template protection, and liveness detection become critical.

For higher-risk transactions, the strongest approach is usually to avoid relying on SMS-based one-time passwords alone and to combine stronger authenticators with step-up controls and monitoring. In some environments, biometric authentication can improve usability but still require a second control for high-value actions. That is why identity assurance guidance from NIST SP 800-63 Digital Identity Guidelines remains central: it helps teams judge not just the method, but the assurance level, recovery process, and fraud exposure around it.

Related resources from NHI Mgmt Group

• When does biometric authentication become a better control than passwords or one-time codes for customer transactions?
• What is the difference between SMS one-time passcodes and mobile network based authentication?
• What is the difference between a PIN and a one-time code?
• What is the difference between passwordless MFA and one-time code MFA?