A team of European researchers has demonstrated a way to check a fingerprint against a watchlist without either party exposing the underlying data, using quantum cryptography to carry out the comparison. The work, published in the journal Scientific Reports, is an early feasibility experiment rather than a deployable product, but it points toward privacy-preserving approaches to identity checks at borders.
The system combines two quantum techniques. Quantum oblivious transfer lets two parties exchange information so that one learns only what it is supposed to and nothing more, while quantum key distribution is used to authenticate the exchange. Both run over a single entanglement-based optical link, with the researchers generating the shared cryptographic material over distances of up to about 25 kilometers of fiber. The goal is to let two sites jointly compute a result without either revealing its private inputs.
Unlike conventional cryptography, which relies on the computational difficulty of solving certain mathematical problems, quantum cryptography exploits the physical properties of quantum particles. Information is encoded in quantum states, such as photons, that cannot be measured or copied without disturbing them, allowing the communicating parties to detect eavesdropping. In this system, those quantum properties are used to distribute cryptographic material and support secure data exchanges, while the fingerprint matching itself still takes place through classical secure-computation techniques running on top of that quantum foundation.
To show how it might be used, the team built a privacy-preserving fingerprint match against a no-fly list for border control. The fingerprint is split into shares held across two separate sites, so no single location holds the complete biometric, and the matching itself is carried out using an established secure-computation protocol supported by the quantum transfer. In their strongest-security configuration, a single match used 128 cryptographic transfers and took about 20 minutes, drawing on cryptographic material prepared in advance to reach roughly nine seconds per transfer. Without that preparation, the researchers reported, each transfer took nearly two minutes, a pace that underscores how far the method is from real-world throughput.
The authors, drawn from the AIT Austrian Institute of Technology, Infineon Technologies Austria, TU Wien, and Portugal’s Instituto de Telecomunicações, present the work as a proof of feasibility for running secure multiparty computation on a quantum physical layer, with support from a European Union quantum research program. It joins a broader effort to match biometric data while keeping it encrypted, seen when Norway tested homomorphic encryption with Mobai for template protection and when Worldcoin rebuilt its iris processing around secure multi-party computation. For now, the quantum approach remains a laboratory demonstration, far slower than conventional matching but aimed at a future where biometric checks leak less data.
Sources: Scientific Reports
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By Cass Kennedy
