QUROPE Quantum Information Processing and Communication in Europe

In this work, the authors study position-based cryptography in the quantum setting. On the negative side, they show that if adversaries are allowed to share an arbitrarily large entangled quantum state, no secure position-verification is possible at all. On the positive side, they show that if adversaries do not share any entangled quantum state but can compute arbitrary quantum operations, secure position-verification is achievable. In models where secure positioning is achievable, it has a number of interesting applications. For example, it enables secure communication over an insecure channel without having any pre-shared key, with the guarantee that only a party at a specific location can learn the content of the conversation. More generally, they also show that in settings where secure position-verification is achievable, other position-based cryptographic schemes are possible as well, such as secure position-based authentication and position-based key agreement.