Uncrackable beams of light

[h1kari]

At toorcon this year there will be a talk on quantum cryptography along  
with a demonstration of some experimental quantum crypto hardware on  
loan from a company in switzerland. Also, there's going to be a really  
good keynote talk by Bruce Schneier of Counterpane and quite a few  
others that look pretty promising (Robert X. Cringely, Cory Doctorow,  
Seth Hardy, etc..). Check out http://www.toorcon.org for more details  
;-).

-h1kari


On Tuesday, Sep 9, 2003, at 19:09 US/Pacific, R. A. Hettinga wrote:

> <http://www.economist.com/science/tq/ 
> PrinterFriendly.cfm?Story_ID=2020013>
>
> The Economist
>
>
>
>
>
>
> MONITOR
>
> Uncrackable beams of light
> Sep 4th 2003
>> From The Economist print edition
>
>
> Quantum cryptography±hailed by theoreticians as the ultimate of  
> uncrackable
> codes±is finally going commercial
>
> IN THE 1992 film 1Ž4Sneakers1Ž2, the ostensible research topic of one  
> of
> the main characters was something called 1Ž4setec astronomy1Ž2. This  
> was an
> anagram of the words 1Ž4too many secrets1Ž2. The research was supposed  
> to
> be about developing a method for decoding all existing encryption  
> codes.
> Well, if that were ever the case, it certainly isn't any more±thanks  
> to a
> start-up in Somerville, Massachusetts, called Magi Q.
>
> Magi Qis in the final stages of testing a system for quantum  
> cryptography,
> which it plans to release commercially within the next few months.
> Encryption engineers have long waxed lyrical about quantum  
> cryptography,
> but this is among the very first commercial implementations. The  
> advantage
> of quantum cryptography schemes is that the code they generate are  
> simply
> not±even in theory±breakable.
>
> The scheme devised by Magi Q, called Navajo, does not use quantum  
> effects
> to transmit the secret data. Instead, it is the keys used to encrypt  
> the
> data that rely on quantum theory. If these keys are changed frequently  
> (up
> to 1,000 times a second in Navajo's case), the risk that an  
> eavesdropper
> without the key would be able to decrypt the data can be proved
> mathematically to be zero. Of course, given the key, the task would  
> become
> a trivial one.
>
> Navajo transmits the changing key sequence over a secure fibre-optic  
> link
> as a stream of polarised photons (indivisible particles of light).  
> Because
> the polarisation reflects the amount of electro-magnetic radiation  
> allowed
> to radiate at an angle to a light beam's direction, it can be  
> considered to
> be a measure of the angular dependence of the light.
>
> Should an eavesdropper tap into the secure fibre-optic line, he would
> disrupt this stream of polarised photons by the very act of observing
> them±and the tampering could be instantly detected. By changing the key
> frequently, Navajo could turn an off-the-shelf encryption scheme such  
> as
> AES (Advanced Encryption System) into something that was essentially
> uncrackable.
>
> As in all good encryption schemes, Navajo employs an element of  
> redundancy.
> The sender has two random-number generators. The first is used to  
> generate
> a random stream of zeros and ones±part of which will form the key. The
> second random-number generator chooses which 1Ž4polarisation basis1Ž2  
> the
> sender will use to transmit a given bit of the key. The sender uses two
> different polarisation bases, which are at right-angles to one another.
> Only by measuring in the correct polarisation basis can a receiver see
> which bit was sent±otherwise the result is meaningless.
>
> For each bit, the receiver arbitrarily chooses which polarisation  
> basis to
> use. The sender and receiver then talk over an open channel and find  
> out
> which bits they measured using the same basis. These bits (about half  
> of
> the total) then constitute the key. If someone has been eavesdropping,  
> some
> of these bits will have been disrupted. In that case the receiver will  
> be
> unable to decode the message, and will thus conclude that someone is
> listening in.
>
> This much is standard quantum cryptography. What is harder is building  
> the
> hardware that can do it quickly and cheaply enough to be commercially
> viable. Magi Qis in a race with a Swiss company called ID Quantique to  
> be
> the first to do so, and currently appears to be in the lead.
>
> Of course, if the quantum signal could be transmitted wirelessly, it  
> would
> liberate users from the cost and constraints of a fibre-optic line. Bob
> Gelfond, Magi Q's founder and chief executive, is coy about the
> possibility. He admits that his firm is working on the idea, but is not
> saying anything at the moment.
>
> For the time being, Navajo requires a dedicated fibre-optic link, which
> only large corporations or governments are likely to have. And it  
> currently
> works only at distances of up to 50 kilometres. Any longer than that  
> and
> random interference degrades the stream of photons and makes them  
> unusable.
> But within these constraints, Navajo is fairly cheap. Magi Qplans to  
> sell
> it for $50,000 a set.
>
> Given the glut of unused optical fibre buried beneath the streets of  
> the
> world, Magi Qis optimistic about Navajo's prospects. Andrew Hammond, a
> vice-president at the company, reckons the market could potentially be
> worth more than $1 billion a year, with much of the business coming  
> from
> firms with valuable intellectual property, such as drugmakers and  
> aircraft
> companies.
>
>
>
> Copyright ' 2003 The Economist Newspaper and The Economist Group. All
> rights reserved.
>
>
>
> -- 
> -----------------
> R. A. Hettinga <mailto: rah at ibuc.com>
> The Internet Bearer Underwriting Corporation <http://www.ibuc.com/>
> 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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--
h1kari <h1kari at dachb0den.com>
Senior Researcher, Dachb0den Labs
http://www.dachb0den.com


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