Noise keeps spooks out of the loop

Tyler Durden camera_lumina at
Tue May 29 05:45:35 PDT 2007

Uh...huh? What if the line is tapped before Bob and Alice start trying to 
communicate on it? The eavesdropper won't be detected.

>From: "R.A. Hettinga" <rah at>
>To: Philodox Clips List <clips at>, cypherpunks at
>Subject: Noise keeps spooks out of the loop
>Date: Sun, 27 May 2007 00:05:32 -0400
>- tech - 23 May 2007 - New Scientist Tech
>Noise keeps spooks out of the loop
>	*	23 May 2007
>	* news service
>	*	D. Jason Palmer
>Enlarge image
>Noise encryption
>SPYING is big business, and avoiding being spied on an even bigger one. So
>imagine if someone came up with a simple, cheap way of encrypting messages
>that is almost impossible to hack into?
>American computer engineer Laszlo Kish at Texas A&M University in College
>Station claims to have done just that. He says the thermal properties of a
>simple wire can be exploited to create a secure communications channel, one
>that outperforms quantum cryptography keys.
>His cipher device, which he first proposed in 2005, exploits a property
>called thermal noise. Thermal noise is generated by the natural agitation
>of electrons within a conductor, which happens regardless of any voltage
>passed through it. But it does change depending on the conductor's
>Kish and his collaborators at the University of Szeged in Hungary say this
>can be used to securely pass information, or an encryption key, down any
>wire, including a telephone line or network cable. In their device, both
>the sender Alice and the receiver Bob have an identical pair of resistors,
>one producing high resistance, the other low resistance. The higher the
>total resistance on the line, the greater the thermal noise.
>Both Alice and Bob randomly choose which resistor to use. A quarter of the
>time they will both choose the high resistor, producing a lot of noise on
>the line, while a quarter of the time they will both choose the low
>resistor, producing little noise. If either detect a high or a low amount
>of noise in the line, they ignore any communication.
>Half the time, however, they will choose differently, producing an
>intermediate level of thermal noise, and it is now that a message can be
>sent. If Bob turns on his high resistor, and records an intermediate level
>of noise, he instantly knows that Alice has chosen her low resistor, in
>essence sending a bit of information such as 1 or 0. Kish's cipher does
>this many times, sending a random series of 1s and 0s that can form the
>basis of an encryption key, the researchers say
>That message is also secure. For a start, as Kish notes, it takes an
>"educated eavesdropper" to even realise information is being sent when
>there seems to be just low-level noise on the line. If they do try to
>eavesdrop, they can only tell a message is being sent, not what it is,
>because it's impossible to tell whether Alice has a high or low resistor
>turned on, and whether the bit of information is a 1 or a 0. What's more,
>eavesdropping on the line will naturally alter the level of thermal noise,
>so Alice and Bob will know that someone is listening in.
>Kish and his team have now successfully built a device that can send a
>secure message down a wire 2000 kilometres long, much further than the best
>quantum key distribution (QKD) devices tried so far. Tests show a signal
>sent via Kish's device is received with 99.98 per cent accuracy, and that a
>maximum of just 0.19 per cent of the bits sent are vulnerable to
>eavesdropping. The error rate is down to the inherent resistance of the
>wire, and choosing a larger wire in future models should help reduce it
>However, this level of security already beats QKD. What's more, the system
>works with fixed lines, rather than the optical fibres used to carry
>photons of light at the heart of quantum encryption devices. It is also
>more robust, as QKD devices are vulnerable to corruption by dust, heat and
>vibration. It is also much cheaper. "I guess it's around a hundred dollars,
>at most," Kish says.
>"This is a system that should be taken seriously," says security specialist
>Bruce Schneier, who founded network security firm BT Counterpane. He says
>he was seduced by the simplicity of the idea when it was first proposed by
>Kish, and now wants to see independent tests of the working model. "I
>desperately want someone to analyse it," he says. "Assuming it works, it's
>way better than quantum."
> >From issue 2605 of New Scientist magazine, 23 May 2007, page 32
>R. A. Hettinga <mailto: rah at>
>The Internet Bearer Underwriting Corporation <>
>44 Farquhar Street, Boston, MA 02131 USA
>"... however it may deserve respect for its usefulness and antiquity,
>[predicting the end of the world] has not been found agreeable to
>experience." -- Edward Gibbon, 'Decline and Fall of the Roman Empire'

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