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Physics Colloquium: Quantum Cryptography using Untrusted Measurement Device

Monday, 07 April, 2014

Quantum Cryptography using Untrusted Measurement Device

Bing Qi, Oak Ridge National Laboratory Quantum Information Science Group

As the Internet and electronic business grows ever more popular, cryptography has become an essential part of our everyday life. Built upon the fundamental laws of quantum mechanics, quantum cryptography (QC), in theory, offers unconditional security (i.e., security against any eavesdropper with unlimited computing power and technological capabilities). However, imperfections in real-life implementations of QC may open a possibility for "side-channel" attacks and thus compromise its unconditional security. Indeed, quantum hacking against practical QC systems, particularly via detector side-channel attacks, has emerged as a hot topic.

In this talk, I will present the basic idea behind quantum key distribution (QKD) protocol arguably the most mature technology in quantum cryptography. I will demonstrate how one can prove its security without knowing what the eavesdropper does. I will also review a few successful quantum hacking schemes and show how small imperfections ignored in the security proof could spoil the security of the whole system. Finally, I will discuss a promising solution to detector side-channel attacks, the so-called measurement-device-independent QKD (MDI-QKD) protocol, which allows QKD users to establish a secure key without trusting their measurement device. This is remarkable because it means that the most expensive and complicated part in a QKD system would no longer require any special security certifications and, in fact, they can even be manufactured and fully controlled by a malicious eavesdropper.




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