148 research outputs found
Security of quantum key distribution with imperfect devices
We prove the security of the Bennett-Brassard (BB84) quantum key distribution
protocol in the case where the source and detector are under the limited
control of an adversary. Our proof applies when both the source and the
detector have small basis-dependent flaws, as is typical in practical
implementations of the protocol. We derive a general lower bound on the
asymptotic key generation rate for weakly basis-dependent eavesdropping
attacks, and also estimate the rate in some special cases: sources that emit
weak coherent states with random phases, detectors with basis-dependent
efficiency, and misaligned sources and detectors.Comment: 22 pages. (v3): Minor changes. (v2): Extensively revised and
expanded. New results include a security proof for generic small flaws in the
source and the detecto
Non-Poissonian statistics from Poissonian light sources with application to passive decoy state quantum key distribution
We propose a method to prepare different non-Poissonian signal pulses from
sources of Poissonian photon number distribution using only linear optical
elements and threshold photon detectors. This method allows a simple passive
preparation of decoy states for quantum key distribution. We show that the
resulting key rates are comparable to the performance of active choices of
intensities of Poissonian signals.Comment: 7 pages, 3 figures, accepted for publication in Opt. Let
Hacking commercial quantum cryptography systems by tailored bright illumination
The peculiar properties of quantum mechanics allow two remote parties to
communicate a private, secret key, which is protected from eavesdropping by the
laws of physics. So-called quantum key distribution (QKD) implementations
always rely on detectors to measure the relevant quantum property of single
photons. Here we demonstrate experimentally that the detectors in two
commercially available QKD systems can be fully remote-controlled using
specially tailored bright illumination. This makes it possible to tracelessly
acquire the full secret key; we propose an eavesdropping apparatus built of
off-the-shelf components. The loophole is likely to be present in most QKD
systems using avalanche photodiodes to detect single photons. We believe that
our findings are crucial for strengthening the security of practical QKD, by
identifying and patching technological deficiencies.Comment: Revised version, rewritten for clarity. 5 pages, 5 figures. To
download the Supplementary information (which is in open access), go to the
journal web site at http://dx.doi.org/10.1038/nphoton.2010.21
Optimum design for BB84 quantum key distribution in tree-type passive optical networks
We show that there is a tradeoff between the useful key distribution bit rate
and the total length of deployed fiber in tree-type passive optical networks
for BB84 quantum key distribution applications. A two stage splitting
architecture where one splitting is carried in the central office and a second
in the outside plant and figure of merit to account for the tradeoff are
proposed. We find that there is an optimum solution for the splitting ratios of
both stages in the case of Photon Number Splitting (PNS) attacks and Decoy
State transmission. We then analyze the effects of the different relevant
physical parameters of the PON on the optimum solution.Comment: Published in the Journal of the Optical Society of America
- …