Quantum Crypto broken again

[mheyman at gmail.com]

A failure in implementation leads to the ability to eavesdrop on a
quantum-secrecy based key exchange on 2/3 of the types of quantum
equipment used.

From: <http://technology.newscientist.com/article/dn14866-laser-cracks-unbreakable-quantum-communications.html>

    Makarov and colleagues from Sweden and Russia have shown that Eve
could control
    Bob's equipment, so that they both decode exactly the same digits
from Alice's
    transmission...The method exploits the way a common type of photon
counter can have
    its sensitivity reduced by a very bright flash of light. The
attack begins when Eve fires a
    pulse of laser light to all four detectors in Bob's
equipment...[Eve leverages this into
    getting the key] by sending on a sequence of encoded photons that
are identical to the
    ones she receives from Alice, Eve can safely intercept a message
without leaving the
    tell-tale quantum errors...Makarov and colleagues have now uncovered such
    vulnerabilities in two of the three types of quantum equipment
commonly used. They
    are now investigating ways to solve the flaw without introducing
more weaknesses.

A paper, "Can Eve control PerkinElmer actively-quenched single-photon
detector?" is available at
<http://arxiv.org/ftp/arxiv/papers/0809/0809.3408.pdf>.

-Michael Heyman

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