U of T researcher uses particles of light to share secret encryption keys

Canada is among several countries researching an encryption technology based on quantum physics that creates decoys to distract hackers from accessing companies’ confidential data. A new quantum cryptography method, designed at the University of Toronto, uses particles of light to share secret encryption keys transmitted over fibre-optic networks. In his study, which was published in the June 16 issue of the Physical Review Letter, U of T professor Hoi-Kwong Lo looked at how senders can vary the intensity of laser light particles or photons used in fibre-optic communications to create decoys that catch eavesdropping attempts.“By increasing the intensity, the sender and the receiver can compare the transmission properties and the error rate,” said Lo, an electrical and computer engineering and physics professor. “By doing that, they can infer what’s going on with the signal depending on the number of photons.”
One photon, for example, means the transmission of the encryption key is secure whereas two or more photons means the communication is not secure.
“By monitoring what’s happening with the weak signal we can see if someone is eavesdropping,” said Lo, also former chief scientist and senior vice-president of Magiq Technologies, which develops quantum information processing solutions.
Bob Gelfond, founder and chief executive officer of the New York-based company, said this type of software is useful to any company trying to protect valuable intellectual property that is typically relayed over private lines from head office to an offsite location.
“Right now those fibres are very easy to tap into,” said Gelfond. “Pretty much anyone with not a lot of ingenuity can put a tap on these fibres and can access very sensitive information.”
According to Lo, the U.S. and European Union governments have put “massive funding” into quantum cryptography. The U.S., he said, has test beds in the U.S. Army Research Lab, NIST (National Institute for Standards and Technology, and at DARPA (Defense Advanced Research Projects Agency).
“Quantum cryptography is ideal for point-to-point ‘dark fibres’ set-ups,” he said. “Suppose a head office is connected directly via dark fibres to a disaster recovery site (for backing up sensitive data). It is important to guarantee perfect security by using quantum cryptography. Experimental quantum cryptography over 100 km of commercial optical fibers has already been performed.”
Alternatives to using quantum-based technology for securing encryption keys like those offered by Magiq — and other companies worldwide like Geneva-based ID Quantique — are expensive and time-consuming, said Gelfond. Some companies use couriers to deliver encryption keys from one location to another while others use a software application to distribute they keys over a virtual private network. The latter method makes it easy for criminals to copy the keys and both make it difficult to change keys frequently, he added.
“(Quantum cryptology) is a paradigm shift,” said Gelfond. “It decreases a fundamental limit on what hackers can do.
“We remove the human element from the security equation. Eliminating the human element increases your level of security.”
U of T received over $1 million in funding for the project from various organizations including the Canadian Institute for Photonic Innovations, Canada Research Chairs program and the Canada Foundation for Innovation (CFI).

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