The impending arrival of the quantum computer will render all existing public-key cryptosystems vulnerable. New solutions are being developed to restore quantum-safe security, i.e. to find new principles and systems which will be resistant against the power of the quantum computer.
Quantum Key Distribution (QKD) is a new way to provide quantum-safe key distribution. The keys can be exchanged between two users in a provably secure manner. They can then be used for all kinds of cryptographic applications.
In a recent article in Science Advances, also reported in Phys.org, a group of scientists at Duke University, The Ohio State University and Oak Ridge National Laboratory propose a new implementation of QKD.
By expanding the space of the photons used in the transmission to higher dimensions, they create so-called qudits, whereby a single photon encodes two bits of information. The transmission protocol is derived from the Coherent-One-Way protocol developed by ID Quantique and the University of Geneva, based on tine-bin encoding of weak pulses.
Their system significantly improves the rate of the key transmission, at the cost of a rather complicated setup, with many optical components and detectors. However, future use of integrated optical devices may turn this interesting experiment into a truly practical solution.
The use of a variety of QKD protocols, in addition to the standard BB84 protocol, may provide advantages for some implementations, and is proof of the maturity of the field. Another significant aspect of the work is the detailed security analysis, which takes into account experimental imperfections, but still provides provable security.
“This type of security analysis reinforces the confidence in practical QKD systems for providing quantum-safe security for commercial applications.” reports Grégoire Ribordy CEO of ID Quantique.