Abstract

We study position-based cryptography in the quantum setting. The aim is to use the geographical position of a party as its only credential. On the negative side, we show that if adversaries are allowed to share an arbitrarily large entangled quantum state, no secure position-verification is possible at all. We show a distributed protocol for computing any unitary operation on a state shared between the different users, using local operations and only one simultaneous round of classical communication. On the positive side, we 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, we show that other position-based cryptographic schemes are possible as well, such as secure position-based authentication and position-based key agreement.

joint work with Harry Buhrman, Nishanth Chandran, Serge Fehr, Ran Gelles, Vipul Goyal and Rafail Ostrovsky.

http://arxiv.org/abs/1009.2490