Custodians who control access to multi-user cryptographic keys are accountable for preventing unauthorized use, but whether they need biometric authentication depends on risk, policy, and legal context. NIST guidance makes clear that strong, multifactor controls reduce compromise: Paul A. Grassi Michael E. Garcia James L. Fenton NIST explain in Special Publication 800-63B that biometrics are an inherence factor that can complement other factors but should not be the sole control because of spoofing, template theft, and irrevocability of biometric data. For key custodians, the priority is enforcing least privilege, auditable access, and cryptographic separation of duties rather than prescribing a single authentication method.
Technical and security considerations
From a technical standpoint, multi-factor authentication that pairs something the custodian knows or has with an inherence factor raises the bar against account takeover. NIST recommends strong authenticators and usage of cryptographic binding between devices and credentials to prevent replay and cloning. For high-value key material, hardware-backed authenticators such as FIDO2 security keys or smart cards provide a stronger assurance of possession than biometrics alone because private keys remain protected in secure elements. Biometrics can strengthen usability and deterrence, but their compromise is permanent and carries higher privacy risk than passwords or tokens.
Operational, legal, and cultural consequences
Mandating biometrics has operational costs: enrollment quality, liveness detection, and fallback processes when readers fail. There are also legal and cultural implications. In jurisdictions with strict data-protection laws, biometric templates are treated as sensitive personal data and require special safeguards and justification. Communities with historical or territorial mistrust of biometric collection may resist mandatory fingerprints or facial scans, affecting workforce relations and compliance. For custodial policies, organizations should perform a risk assessment tied to key sensitivity, document chain-of-custody controls, and prefer cryptographic, hardware-backed measures where possible.
In practice, custodians do not universally need biometric authentication; instead, they need a layered approach tailored to the asset value and regulatory context. Combining hardware-backed possession factors, strong PINs or passphrases, robust logging, and periodic key rotation often delivers better security and privacy trade-offs than relying solely on biometric checks. When biometrics are used, treat them as one component within a defensible, auditable access-control design rather than a single point of trust.