Applied Physics

Eavesdropping Foiled by Decoys

Science  19 Jan 2007:
Vol. 315, Issue 5810, pp. 303
DOI: 10.1126/science.315.5810.303a

Secure communication between a sender and a receiver generally requires the message to be encrypted, with the sender and recipient sharing a secret key that encodes and deciphers the message. Ideally, the key should be changed often, and so for practical reasons the key should be distributable over normal communication channels. However, the possibility of the interception of the key by an eavesdropper would compromise security. There is, therefore, a need for a method to distribute the key to the recipient securely so that any attack on the communication channel by a potential eavesdropper can be detected and appropriate action taken.

Yuan et al. use a combination of signal and decoy optical pulses sent over a 25-km optic fiber to demonstrate unconditionally secure quantum-key distribution to a recipient. Because the decoy pulses are weaker than the signal pulses, interception by an eavesdropper considerably reduces their transmission rate to the receiver, thereby revealing the existence of an eavesdropper. Although the use of decoy pulses does provide for secure communication, it also places stringent requirements on the calibration of the sources and the detectors so that artifacts do not compromise security. — ISO

Appl. Phys. Lett. 90, 011118 (2007).

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