Inside Quantum Technology

Chinese Researchers Hack Device-Independent Quantum Cryptography

(TechnologyReview) Xiao-Ling Pang and colleagues at Shanghai Jiao Tong University in China say they have managed to hack device-independent quantum cryptography with a frighteningly high success rate.
Most quantum encryption systems encode information using photons. Various cybersecurity researchers have found ways to hack this kind of system. A shortcoming they’ve exploited is that the data is often encoded in the polarization of a photon. One hack is to shine a high-powered laser into the equipment so that it reflects off the polarizers inside. The reflections reveal the orientation used to polarize and encode the outgoing photons. And that reveals the code.
Pang and colleagues, who say they’ve found an entirely new way to attack quantum communication that doesn’t rely on reflections. The new technique hinges instead on an effect called injection locking. This is a method of changing the frequency of a laser by injecting photons with a different seed frequency into the lasing cavity. Pang and co say they’ve tested the approach with remarkable results.

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