Autumn 2005 / Leading Edge
Foiled Again

Prof develops quantum cryptography method that could improve Internet security


Hackers, beware: a new quantum-cryptography method designed at U of T may soon increase Internet-communication security.

Quantum cryptography uses particles of light to share encryption keys relayed through fibre optic communications. A paper published in Physical Review Letter demonstrates how senders can vary the intensity of laser light particles (photons) to create decoys that catch eavesdropping attempts.

This new technique manipulates a laser to create different signals of various intensities. The signals act as decoys to distract the eavesdropper from the message containing the encryption key. “Any attack will necessarily affect the decoy states and therefore be caught by the legitimate users, who will then use an encryption key only when it is guaranteed to be secure,” says the study’s lead author Professor Hoi-Kwong Lo of U of T’s department of electrical and computer engineering and department of physics


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