Hacking quantum crypto not blindingly obvious after all

Hacking quantum crypto not blindingly obvious after all

Summary: A recently proposed physical attack on a quantum cryptography system has been comprehensively rejected by researchers at Toshiba in Cambridge, who say that as long as the kit is all operating correctly, the so-called 'blinding' attack will not work.

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TOPICS: Graphene
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A recently proposed physical attack on a quantum cryptography system has been comprehensively rejected by researchers at Toshiba in Cambridge, who say that as long as the kit is all operating correctly, the so-called 'blinding' attack will not work.

The protocols of quantum crypto are as safe as they ever were; any attempt to eavesdrop on the exchange of the keys to the cipher will disrupt the transmission, alerting the recipient that the message has been compromised and preventing the key exchange.

Faced with these impenetrable protocols, the Norwegian researchers focused their efforts on the physical system. They came up with the notion of ‘blinding’ the message detector - known as an avalanche photo detectors - with a bright laser beam. They contended that this would disrupt the hardware enough that errors thrown up by the act of eavesdropping would be lost in the noise. An eavesdropper could read off the keys, undetected.

However, the researchers at Toshiba’s Cambridge labs have challenged the attack in a letter published in the December issue of Nature Photonics. They say the hack would only work if a system had not been properly implemented:

"The attack will be ineffective on most single photon avalanche photodiodes (APDs) and certainly ineffective on any detectors that are operated correctly," the researchers write. "The attack is only successful if a redundant resistor is included in series with the APD, or if the detector discrimination levels are set inappropriately."

Further, the researchers say, the hack as described can be prevented by simply monitoring the photocurrent generated by the detector.

Those with access can read more from Nature Photonics here

Topic: Graphene

Lucy Sherriff

About Lucy Sherriff

Lucy Sherriff is a journalist, science geek and general liker of all things techie and clever. In a previous life she put her physics degree to moderately good use by writing about science for that other tech website, The Register. After a bit of a break, it seemed like a good time to start blogging about weird quantum stuff for ZDNet. And so here we are.

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2 comments
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  • The team at Toshiba has ignored variants of our attack published two weeks after our original Nature Photonics publication and two weeks before they published their comment. Specifically, there are:

    After-gate attack
    http://arxiv.org/abs/1009.2683

    Thermal blinding attack, Sinkhole attack
    http://arxiv.org/abs/1009.2663

    Of these three attacks, two (after-gate and sinkhole) should work perfectly on Toshiba's "hack-proofed" detector. 1.5 months ago I contacted Andrew Shields and asked if I could come to Cambridge with our equipment and confirm/demonstrate this on their detector. He refused. They carefully avoid mention of these two likely-to-work attacks in their published comment.

    We have detailed this in our reply http://arxiv.org/abs/1012.0476 but journalists just seem to read Toshiba's press release and not the correspondence published in Nature Photonics.
    Vadim Makarov
  • Hi Makarov - I'll put his to Toshiba. Will let you know what they say.

    Lucy
    Lucy Sherriff