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June 16, 2013

Digital Cloaking: Invisible electronic communications are here — talk about timely

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Below, excerpts from Daniel Akst's story in yesterday's Wall Street Journal:

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For now at least, Harry Potter's cloak of invisibility remains a fantasy. But scientists have been working for several years on ways of rendering objects invisible.

Now researchers at Purdue University have come up with a way to do much the same for electronic communications. They have been using a technique known as "temporal cloaking," which they have made so much more effective that commercial applications begin to seem plausible.

These days, communications are heavily dependent on fiber-optic lines, which transmit messages as pulses of light. Relying on equipment already in common use, the Purdue scientists modulated the timing of light pulses to cover them up. At the receiving end, additional modulators uncloak the pulses by filling the light back in, effectively deciphering them.

It's called temporal cloaking because it occurs over time. That compares with "spatial" cloaking, which relies on special materials to render objects—so far, only very tiny ones—invisible. Earlier efforts cloaked far less than 1% of the transmission time for optical communications. The Purdue scientists have bumped that up to 46%, and report that 90% should be possible.

The technique ought to apply to any communication sent over a fiber optic line, since voice, video and Internet data are all reduced to pulses of light for efficient transmission. Theoretically, temporal cloaking is better than even the strongest encryption because it can render the very existence of a communication undetectable.

Given recent revelations that the National Security Agency is collecting data on telephone calls and monitoring the Internet communications of foreign targets, temporal cloaking raises some provocative questions. If it reaches commercialization, for example, who will be allowed to use it?

Temporal cloaking looks to be a significant technological move in the never-ending chess game between the forces of privacy and those of surveillance. Neither side is likely to achieve checkmate anytime soon.

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Below, the Nature abstract of the paper cited above.

A temporal cloak at telecommunication data rate

Through advances in metamaterials — artificially engineered media with exotic properties, including negative refractive index — the once fanciful invisibility cloak has now assumed a prominent place in scientific research. By extending these concepts to the temporal domain, investigators have recently described a cloak which hides events in time by creating a temporal gap in a probe beam that is subsequently closed up; any interaction which takes place during this hole in time is not detected. However, these results are limited to isolated events that fill a tiny portion of the temporal period, giving a fractional cloaking window of only about 10−4 per cent at a repetition rate of 41 kilohertz — which is much too low for applications such as optical communications. Here we demonstrate another technique for temporal cloaking, which operates at telecommunication data rates and, by exploiting temporal self-imaging through the Talbot effect, hides optical data from a receiver. We succeed in cloaking 46 per cent of the entire time axis and conceal pseudorandom digital data at a rate of 12.7 gigabits per second. This potential to cloak real-world messages introduces temporal cloaking into the sphere of practical application, with immediate ramifications in secure communications.

June 16, 2013 at 08:01 PM | Permalink


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