Position-based quantum cryptography: A scientific breakthrough?

Position-based quantum cryptography is a discovery that could lead to more secure communications, especially between devices used on military bases and satellites, based on using the geographical position of a party as its only credential, according to new research.

“There is a lot of need for position-based cryptography,” says Rafail Ostrovsky, a computer scientist and researcher at University of California, Los Angeles (UCLA). “The new discovery here is how to exchange a key relying on quantum physics.”

Ostrovsky is co-author of the paper “Position-Based Quantum Cryptography,” which will be presented at the 51st Annual IEEE Symposium on Foundations of Computer Science which takes place in October in Las Vegas.

The paper puts forward theoretical research in math and cryptography used in quantum physics to show it’s possible to provide better security than more traditional cryptographic methods and position-pinpointing triangulation. Quantum cryptography makes use of quantum systems to do cryptographic tasks, and what Ostrovsky and his fellow researchers are proposing is a theoretical foundation for sending quantum bits to establish a key-exchange protocol based solely on location.

The idea, Ostrovsky says, is to be able to pinpoint location in three-dimensional space to securely communicate only with the device that is there. But he notes that research done last year has shown the classic triangulation techniques with classic cryptography are not reliably secure and can be spoofed by an adversary.

“There are hundreds of papers written in this area, but we proved none of these methods work,” Ostrovsky says.

The new paper was co-authored with UCLA researchers Nishanth Chandran and Ran Gelles, along with Vipul Goyal, a former UCLA student who now works at Microsoft Research India and Serge Fehr, scientific staff member with the Cryptology and Information Security Group at CWI in The Netherlands. A grant from the National Science Foundation helped support the work.

The work of the researchers may certainly be challenged and argued when it’s presented at the IEEE Symposium on Foundations of Computer Science later in October, but Ostrovsky says he welcomes any critique.

“It is impossible to disprove a mathematical equation, unless there is an error,” he notes. “So I think this is a development in theoretical science that will not be disproved. This is how progress in science is made, as we learn more and more of the facts that can not be refuted.”

If the work outlined in the paper holds up under criticism, there’s still the question of whether it will be implemented in any practical use. While that may be a ways off, Ostrovsky says he has already fielded inquiries from some in the U.S. government who want to know how it could work.

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