Quantum position-based cryptography

by Dr Andreas Bluhm (Uni Grenoble Alpes, CNRS)

Thursday 14 Nov 2024, 16:15 → 17:30 Europe/Berlin

D 114 (ENC)

Imagine that you sit in front of a computer and look at a website that looks like the website of your bank. But how can you be sure that it is genuine? If you could verify that the server is indeed in the basement of the bank, you could stop worrying. This is the idea behind position-based cryptography: The position of a party is used as a credential. We put forward the hitherto simplest protocol for quantum position verification and prove that it is secure as long as the attackers have at most an amount of qubits linear in the classical information sent during the protocol, while the honest parties only need a single qubit. Moreover, we prove that adding a commitment step, we can prove security of this simple protocol against arbitrary photon loss, thereby exhibiting the first protocol that is both secure against photon loss, secure against entangled attackers, can allow the quantum information to travel slowly, and is simple for the honest parties. This solves a big challenge on the way towards practical protocols for secure quantum position-verification, as in experimental setups, e.g. using fiber optics, most of the photons sent get lost, which can compromise security.

Einladende: Ramona Wolf