Venus AUEB Forum

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One of the biggest commercial uses for quantum cryptography to date has been to securely exchange keys. Unlike traditional key distribution techniques, using quantum mechanics offers a seemingly foolproof upside: any attempt by an attacker to measure quantum data disturbs it -- per the Heisenberg uncertainty principle -- which a quantum cryptography system can detect, thus ensuring that communications remain secure.

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According to Gerd Leuchs, who's part of the research team, "the security of quantum cryptography relies on quantum physics but … it must also be properly implemented." In other words, any system may have implementation loopholes. The attack works by blinding the photon detector with a bright light -- the laser. Over its continuous wave of light, the researchers then added even stronger laser pulses to transmit data, but in a way that the quantum cryptography security system can't detect, because it doesn't involve quantum mechanics

The researchers reported their findings in an advance online version of Nature Photonics, released last week. "Based on these experimental results," they write, someone "can attack the systems with off-the-shelf components, obtaining a perfect copy of the raw key without leaving any trace of her presence." With the key in hand, communications between the two key sharers could then be intercepted and decrypted, again without either party knowing.