With the revelation that the NSA has been collecting phone call data about Verizon users, it’s a good time to think about new ways to secure data communications. And researchers at Purdue have developed a fascinating type of security that has the potential to be implemented on a large scale: they’ve built a “temporal cloak” that can hide communications by building a “hole in time.” This research builds on work being done at Cornell that was first reported in the summer of 2011.
The previous temporal cloak, however, was limited in nature – it was only able to hide discrete events for a few seconds at a time and required specialized equipment. The new cloak, however, can hide data long enough to transmit over fiber-optics. What’s more, it was built using off-the-shelf components “that could integrate smoothly into the existing telecommunications infrastructure,” according to researcher Joseph Lukens.
A phase shift (Credit: Wikipedia)
To be clear, saying that these researchers have built a “hole in time” doesn’t mean that they’ve literally manipulated space-time, Time Lord style. It has to do with how light works over fiber-optic networks. In a fiber-optic network, data is communicated in ones and zeros that are represented by pulses of light. One piece of equipment that can be employed with fiber-optic networks is a phase modulator. The equipment modulates the timing of light waves of the same frequency. Two waves of light of the same frequency are out of phase to the degree that they are located in different positions at any given time. (The figure to the right shows an example of a phase shift.)
In other words, the phase of a light wave determines to what degree that it interferes with another. Mathematically, the phase of the light wave is a measure of time, rather than space. So when two light waves are phased such that one wave is at its positive maximum, while the other is at its negative maximum, the two waves cancel each other out – which makes it look like a flat line. On a fiber-optic line, that interference can be created with a phase modulator.
Using two phase modulators, the researchers were able to create such interference, which marked the beginning of the cloak. They then sent data over the network, and used two more phase modulators to again create temporal interference, which marks the end of the cloak. Basically, they create a “hole in time” that can be used to hide data.
Normally, when data is being sent over a fiberoptic line, there’s a visible voltage signal that can be detected. But when you turn on the cloak, as the researchers noted in the paper, the signal will “reduce to a single flat line, and the data are effectively cloaked. This temporal cloak consequently succeeds in hiding communications at will, by simply turning four phase modulators on and off.”
In practice, this system isn’t perfect. Although the researchers were able to hide all the transmitted data, they were only able to use about “46% of all the time slots available for sending the data,” Lukens told me. But according to their research, “future cloaks based on our arrangement have the potential for significant improvements, both in terms of operational bandwidth and the duration of the cloaked region.”
To get those improvements, it’s necessary for some current technology to improve. In particular, the phase modulators themselves, which can cause some “temporal distortions.” However, the researchers suggest a method by which the cloak could be improved without advanced technology. Using that method could create a “cloaking window of over 90%,” according to the paper. If successful, that would mean that you’d be able to package more data into a temporal cloak.
The bottom line, though, is that this is a feasible security technology in the long run just by refining our current technology. As the researchers note in the paper, achieving a full cloak “remains a possibility for the future; nothing inherently prevents it.”
Which means that there may come a day when you’re able to transmit information that not only can’t be intercepted by a spy, but also without that spy being able to tell that you sent a message in the first place.
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