Tuesday, December 11, 2012

Researchers discover new quantum encryption method to foil hackers

Researchers discover new quantum encryption method to foil hackers April 2, 2012 A research team led by University of Toronto Professor Hoi-Kwong Lo has found a new quantum encryption method to foil even the most sophisticated hackers. The discovery is outlined in the latest issue of Physical Review Letters. Ads by Google Construction Laser Repair - Repairing Most All Brands 30 Years of Repair Experience - Quantum cryptography is, in principle, a foolproof way to prevent hacking. It ensures that any attempt by an eavesdropper to read encoded communication data will lead to disturbances that can be detected by the legitimate users. Therefore, quantum cryptography allows the transmission of an unconditionally secure encryption key between two users, "Alice" and "Bob," in the presence of a potential hacker, "Eve." The encryption key is communicated using light signals and is received using photon detectors. The challenge is that Eve can intercept and manipulate these signals. "Photon detectors have turned out to be an Achilles' heel for quantum key distribution (QKD), inadvertently opening the door to subtle side-channel attacks, most famously quantum hacking," wrote Dr. Charles Bennett, a research fellow at IBM and the co-inventor of quantum cryptography. When quantum hacking occurs, light signals subvert the photon detectors, causing them to only see the photons that Eve wants Bob to see. Indeed, earlier research results by Professor Lo and independent work by Dr. Vadim Makarov of the Norwegian University of Science and Technology have shown how a clever quantum hacker can hack commercial QKD systems. Now, Professor Lo and his team have come up with a simple solution to the untrusted device problem. Their method is called "Measurement Device Independent QKD." While Eve may operate the photon detectors and broadcast measurement results, Bob and Alice no longer have to trust those measurement results. Instead, Bob and Alice can simply verify Eve's honesty by measuring and comparing their own data. The aim is to detect subtle changes that occur when quantum data is manipulated by a third party. Specifically, in Measurement Device Independent QKD, the two users send their signals to an untrusted relay – "Charlie" – who might possibly be controlled by Eve. Charlie performs a joint measurement on the signals, providing another point of 

comparison. "A surprising feature is that Charlie's detectors can be arbitrarily flawed without compromising security," says Professor Lo. "This is because, provided that Alice and Bob's signal preparation processes are correct, they can verify whether Charlie or Eve is trustworthy through the correlations in their own data following any interaction with Charlie/Eve." A proof-of-concept measurement has already been performed. Professor Lo and his team are now developing a prototype measurement device independent QKD system, which they expect will be ready within five years. As a result of implementing this new method, quantum cryptography's Achilles' heel in the fight against hackers has been resolved. Perhaps, a quantum jump in data security has now been achieved.
 How to remove detector side channel attacks has been a notoriously hard problem in quantum cryptography. Here, we propose a simple solution to this problem—measurement-device-independent quantum key distribution (QKD). It not only removes all detector side channels, but also doubles the secure distance with conventional lasers. Our proposal can be implemented with standard optical components with low detection efficiency and highly lossy channels. In contrast to the previous solution of full device independent QKD, the realization of our idea does not require detectors of near unity detection efficiency in combination with a qubit amplifier (based on teleportation) or a quantum nondemolition measurement of the number of photons in a pulse. Furthermore, its key generation rate is many orders of magnitude higher than that based on full device independent QKD. The results show that long-distance quantum cryptography over say 200 km will remain secure even with seriously flawed detectors.

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