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Quantum Hackers: Cracking the ­ncrackable Code

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Quantum Cryptography Scheme

Inside a quantum cryptography scheme at Norwegian University of Science and Technology.

Credit: Courtesy of Vadim Makarov

Norwegian University of Science and Technology researcher Vadim Makarov has developed a quantum cryptography method to defend against attacks of quantum key distribution (QKD) systems.

To search for weaknesses in QKD systems, Makarov's team investigated the detectors that would be used by two imaginary figures to send a secret key. Most systems use an avalanche photodiode detector, which generates an electrical pulse when it receives a single photon.

Makarov's team found they could blind the detectors with a short pulse of bright light, raising the detectors' threshold so that they no long responded to single photons. Ludwig Maximillians University researcher Harald Weinfurter found that by sending a small pulse of light into built-in gaps in some detectors, they could temporarily blind one of the imaginary figures just before each signal is sent without being detected. By repeating the process, the researchers can dictate exactly which digits the key will include.

From New Scientist
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