By Alexandra Burlacu | Nov 20, 2012 09:36 AM EST
Internet security is paramount in today's tech-driven world, and scientists have now perfected a cheaper technique to protect telecom networks using quantum cryptography.
Scientists at Toshiba and Cambridge University have discovered a less expensive alternative to ensure the security of the high-speed fiber optic cables that stand at the basis of the modern Internet.
The technique is designed to capture pulses of quantum light hidden in streams of billions of photons, transmitted each second through data networks, by making infinitesimally short time measurements.
Scientists extracted weak photons from the torrents of light pulses transmitted through data networks by using an advance photodetector, thus making it possible to safely carry secret keys needed to scramble data over extended distances of up to 56 miles.
While such data scrambling systems will likely find their primary applications in government communications systems for national security, they can also be of great value for protecting financial data and virtually all information transmitted online.
The innovative approach is based on quantum physics, which allows for the exchange of information in a way that would make eavesdropping on the communication immediately obvious. The technique requires the ability to measure an indefinitely small window of time to capture a pulse of light. In this case, that window of time lasted only 50 picoseconds, which would equal the time it takes light to travel 15 millimeters.
Safely exchanging encryption keys used to scramble and unscramble data is one of the most frustrating aspects of modern cryptography. Public key cryptography, for instance, uses a key that is publicly distributed, and another related secret key that remains private, allowing two people communicating virtually to safely exchange information. Such systems, however, have several vulnerabilities, and some computers may be powerful enough to decode data encrypted with mathematical formulas.
The possibility of reliably exchanging information means it is also possible to use the so-called one-time pad encryption system, which is one of the most secure forms.
According to Andrew J. Shields, assistant managing director for Toshiba Research Europe and one of the authors of the research paper, several commercially available quantum key distribution systems already exist. Those systems, however, rely on the necessity of transmitting the quantum key separately from communication data, often in a separate optical fiber. This, in turn, leads to more expenses by adding significant costs and complexity to the cryptography systems that protect the high-speed information flowing over fiber optic networks.
Scientists believe that bundling quantum information into traditional networking data will not only lower the cost, but also simplify the task of coding and decoding the data. The method would also make quantum key distribution systems more appealing for commercial data networks, added the authors.
While modern optical data networking transmits multiple data streams simultaneously in different colors of light to increase capacity, the Toshiba-Cambridge system sends the information over the same fiber, but creating its own frequency to isolate it.
"The requirement of separate fibers has greatly restricted the applications of quantum cryptography in the past, as unused fibers are not always available for sending the single photons, and even when they are, can be prohibitively expensive. Now we have shown that the single photon and data signals can be sent using different wavelengths on the same fiber," said Dr. Shields.
"We can pick out the quantum photons from the scattered light using their expected arrival time at the detector. The quantum signals hit the detector at precisely known times - every one nanosecond, while the arrival time of the scattered light is random."
Fiber-optic cables can carry great amounts of data, but they are also highly insecure. According to Shields, all an eavesdropper needs is to bend a cable and expose a fiber, which makes it possible to capture light leaking from the cable and convert it into digital ones and zeros.
"The laws of quantum physics tell us that if someone tries to measure those single photons, that measurement disturbs their state and it causes errors in the information carried by the single photon. By measuring the error state in the secret key, we can determine whether there has been any eavesdropping in the fiber and in that way directly test the secrecy of each key."
Zhiliang Yuan, who worked on the research, told Reuters that his team plans to carry out test field on the system, and it should become commercially available within a few years.
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