Biometric Data Security (2)

Protecting biometric data requires a multilayered approach combining secure design, cryptographic protections, good operational practices and a regulatory framework. Protecting this type of data therefore demands very particular rigour. As we saw in our first part, because it relies on permanent bodily characteristics, this data cannot be reset in the event of a leak. Securing it therefore requires an approach that combines minimized collection, a robust technical architecture, advanced cryptography and rigorous legal governance.

In this second part, we will look at the technical, organizational and legal best practices for protecting biometric data.

Minimize Collection and Limit Uses

The fundamental principle is to collect biometric data only if its storage is strictly necessary. Minimizing collection remains the best protection. If biometrics is not essential, alternative authentication factors should be preferred (strong passwords, physical keys, limited-use authentication).
Every piece of biometric data collected represents a lasting responsibility for the organization that collects it, and restricting the amount collected and stored mechanically reduces the risk.

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Store, but in a Controlled Way

Storing raw data must be avoided. The biometric capture must systematically be converted into a template, ideally a cancelable one.
Template protection techniques include:

• irreversible transformations that prevent any reconstruction of the original biological signal;

• dedicated cryptographic schemes

• hashing methods suited to the biometric context.

• Keeping the template locally and never allowing it to end up in clear text on a server.

Use Advanced Cryptography

Certain cryptographic approaches make it possible to go further. Comparisons using homomorphic encryption or secure multiparty computation (MPC) make it possible to verify identity without decrypting the data on a third-party server.
These solutions remain resource-intensive, but they are particularly well suited to sensitive environments (banks, public institutions, defence). Privacy-preserving biometric matching methods are maturing and should be favoured for critical applications and institutions.

Ensure Resistance to AI Attacks

Liveness detection aims to verify that the data comes from a real person who is present at the time of capture.
This barrier remains effective against artifact attacks (masks, photographs, recordings).
However, the rise of AI-generated image and sound generators calls for heightened vigilance: fake streams are becoming more and more realistic.
Systems must therefore combine several indicators: texture analysis, micro-expressions, dynamic interactions, and evolve continuously to counter new forgery techniques.

Build Protection In from the Design Stage

A protection-by-design approach must be built in from the earliest phases of the project.
This implies:

• explicit and adjustable consent mechanisms;

• a strictly limited retention period;

• secure archiving;

• and above all, a functional separation between identifiers and biometric templates.

Auditability is just as essential: immutable access logs, traceability of processing and regular checks ensure compliance and make it easier to detect anomalies.

Legal Framework and Regulatory Compliance

Biometric data is classified among the sensitive categories by most regulators.

In the European Union, for example, the General Data Protection Regulation (GDPR) imposes strict conditions on its processing:

• a solid legal basis,
• clear information for the individuals concerned
• informed collection of consent,
• and secure storage, which notably requires appointing a person specialized in data protection and carrying out regular impact assessments.

Article 9 of the GDPR notably prohibits its processing except in limited cases (public security, public interest, explicit consent).

Authorities such as the CNIL point out that consent alone is not enough if there is no non-biometric alternative. Data protection impact assessments (DPIAs) are systematically required for facial recognition, secure access or identity control systems.

This regulatory tightening reflects a growing awareness: biometrics must not become a surveillance tool, but a proportionate, transparent identification mechanism that is reversible in its effects.

In the United States, Illinois's Biometric Information Privacy Act (BIPA) imposes written consent requirements and provides for severe civil penalties for non-compliance.
The lawsuits brought against Facebook and Clearview AI marked a turning point, showing that judicial pressure could force the tech giants to review their practices for collecting and retaining biometric data.

Anticipate: Revocability and Incident Response

Because a fingerprint cannot be replaced, systems must be designed to be cancelable.
The principle is to apply an irreversible, configurable transformation to the biometric template: in the event of a compromise, this transformation can be revoked and a new one generated, without modifying the original biological data (which would obviously be impossible).
This logic of a derived, renewable identifier offers better resilience against leaks.

Any organization that processes biometric data must have a specific incident response plan.
It must describe:

• the assessment and containment steps;

• prompt notification of the authorities and the individuals concerned;

• revocation and replacement of the associated keys or transformations;

• and the setting up of support for victims (monitoring, legal assistance).

Public communication must be fast and transparent, but measured: disclosing too much technical information could facilitate new attacks.

Biometric data offers undeniable advantages for authentication and user experience.
But its permanent nature demands very strict security. One simple rule prevails: never depend exclusively on biometrics. For organizations, one essential rule must be remembered: design systems as if they could be compromised, and plan the necessary mitigation and remediation mechanisms from the design stage. Join us in December for our new theme. In the meantime, if you have a film, a series, software or an ebook to protect, don't hesitate to call on our services by contacting one of our account managers; PDN has been a pioneer in cybersecurity and anti-piracy for more than ten years, and we certainly have a solution to help you. Happy reading, and see you soon!

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