Secure positioning: impossible or possible?


Is quantum information the promising solution for position-based cryptography? In their paper ‘Position-based Quantum Cryptography, Impossibility and Constructions’ that was published at the CRYPTO 2011 conference, researchers Harry Buhrman and Serge Fehr from the Centrum Wiskunde & Informatica (CWI) in Amsterdam, Christian Schaffner from the University of Amsterdam (UvA) and researchers from the University of California, Los Angeles (UCLA) and Microsoft Research India come one step closer to finding the answer to this challenging question. Gilles Brassard, pioneer in quantum cryptography, reviews today on this interesting line of research in Nature News & Views,  (edition 17 November 2011).

In their work, the researchers study position-based cryptography in the quantum setting. In position-based cryptography the geographical position of a person acts as the ‘key’ for accessing secured data and services. The research of Buhrman and his colleagues shows now that quantum informatics cannot provide a secure solution for position-based cryptography. They prove that based on quantum teleportation, (the process by which a qubit can be transmitted instantaneously from one location to another) all attempts to provide a secure method for position-based cryptography are doomed to failure. This breakthrough comes as a surprise, since it was expected that it was possible to build secure schemes.

The interesting challenge remains whether it is possible to design schemes for location-based cryptography that are provable secure in a realistic setting, where quantum resources of the opponent are limited. The possibility of location-based cryptography offers a number of interesting applications. For example banks and the military could benefit significantly from a method like location-based secure communication that enables that only the person at a specific location can learn a secured message.

The article appeared 17 November in Nature, pages 307-308, Volume 479.

Related CWI press release: