6,627 research outputs found
Attacking practical quantum key distribution system with wavelength dependent beam splitter and multi-wavelength sources
Unconditional security of quantum key distribution protocol can be guaranteed
by the basic property of quantum mechanics. Unfortunately, the practical
quantum key distribution system always have some imperfections, and the
practical system may be attacked if the imperfection can be controlled by the
eavesdropper Eve. Applying the fatal security loophole introduced by the
imperfect beam splitter's wavelength dependent optical property, we propose
wavelength-dependent attacking model, which can be applied to almost all
practical quantum key distribution systems with the passive state modulation
and photon state detection after the practical beam splitter. Utilizing our
attacking model, we experimentally demonstrate the attacking system based on
practical polarization encoding quantum key distribution system with almost
100% success probability. Our result demonstrate that all practical devices
require tightened security inspection for avoiding side channel attacks in
practical quantum key distribution experimental realizations
Phase encoding schemes for measurement device independent quantum key distribution and basis-dependent flaw
In this paper, we study the unconditional security of the so-called
measurement device independent quantum key distribution (MDIQKD) with the
basis-dependent flaw in the context of phase encoding schemes. We propose two
schemes for the phase encoding, the first one employs a phase locking technique
with the use of non-phase-randomized coherent pulses, and the second one uses
conversion of standard BB84 phase encoding pulses into polarization modes. We
prove the unconditional security of these schemes and we also simulate the key
generation rate based on simple device models that accommodate imperfections.
Our simulation results show the feasibility of these schemes with current
technologies and highlight the importance of the state preparation with good
fidelity between the density matrices in the two bases. Since the
basis-dependent flaw is a problem not only for MDIQKD but also for standard
QKD, our work highlights the importance of an accurate signal source in
practical QKD systems.
Note: We include the erratum of this paper in Appendix C. The correction does
not affect the validity of the main conclusions reported in the paper, which is
the importance of the state preparation in MDIQKD and the fact that our schemes
can generate the key with the practical channel mode that we have assumed.Comment: We include the erratum of this paper in Appendix C. The correction
does not affect the validity of the main conclusions reported in the pape
Postponement of dark-count effects in practical quantum key-distribution by two-way post-processing
The influence of imperfections on achievable secret-key generation rates of
quantum key distribution protocols is investigated. As examples of relevant
imperfections, we consider tagging of Alice's qubits and dark counts at Bob's
detectors, while we focus on a powerful eavesdropping strategy which takes full
advantage of tagged signals. It is demonstrated that error correction and
privacy amplification based on a combination of a two-way classical
communication protocol and asymmetric Calderbank-Shor-Steane codes may
significantly postpone the disastrous influence of dark counts. As a result,
the distances are increased considerably over which a secret key can be
distributed in optical fibres reliably. Results are presented for the
four-state, the six-state, and the decoy-state protocols.Comment: Fully revised version (12 pages and 8 figures). Improved figures and
discussion added. To appear in Eur. Phys. J.
Measurement-device-independent quantum communication with an untrusted source
Measurement-device-independent quantum key distribution (MDI-QKD) can provide
enhanced security, as compared to traditional QKD, and it constitutes an
important framework for a quantum network with an untrusted network server.
Still, a key assumption in MDI-QKD is that the sources are trusted. We propose
here a MDI quantum network with a single untrusted source. We have derived a
complete proof of the unconditional security of MDI-QKD with an untrusted
source. Using simulations, we have considered various real-life imperfections
in its implementation, and the simulation results show that MDI-QKD with an
untrusted source provides a key generation rate that is close to the rate of
initial MDI-QKD in the asymptotic setting. Our work proves the feasibility of
the realization of a quantum network. The network users need only low-cost
modulation devices, and they can share both an expensive detector and a
complicated laser provided by an untrusted network server.Comment: 13 pages, 4 figures. arXiv admin note: the security proof technique
is based on arXiv:0802.2725, arXiv:0905.4225
Implementation vulnerabilities in general quantum cryptography
Quantum cryptography is information-theoretically secure owing to its solid
basis in quantum mechanics. However, generally, initial implementations with
practical imperfections might open loopholes, allowing an eavesdropper to
compromise the security of a quantum cryptographic system. This has been shown
to happen for quantum key distribution (QKD). Here we apply experience from
implementation security of QKD to several other quantum cryptographic
primitives. We survey quantum digital signatures, quantum secret sharing,
source-independent quantum random number generation, quantum secure direct
communication, and blind quantum computing. We propose how the eavesdropper
could in principle exploit the loopholes to violate assumptions in these
protocols, breaking their security properties. Applicable countermeasures are
also discussed. It is important to consider potential implementation security
issues early in protocol design, to shorten the path to future applications.Comment: 13 pages, 8 figure
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