Quantum crypto news

[1.26.2005] Creation of a polarization W state using optical fibre multiports

2005-01-26T03:36:00.000Z

Journal of Modern Optics
Issue: Volume 52, Number 5 / March 20, 2005
Pages: 755 - 761
URL: JMO52.0755, 2005
DOI: 10.1080/09500340412331289565

Creation of a polarization W state using optical fibre multiports

Bao-Sen Shi and Akihisa Tomita
A1 Imai Quantum Computation and Information Project NEC Tsukuba Laboratories ERATO Japan Science and Technology Agency (JST) Fundamental Research Laboratories NEC 34 Miyukigaoka Tsukuba Ibaraki 305-8501 Japan

Abstract:
A scheme for experimental creation of a polarization W state is reported in this paper. This scheme is based on a common commercial multiport fibre coupler and single photon source and it is feasible using current technology. This scheme has a higher efficiency and can be easily extended to generate a multiphoton W state with a photon number larger than 4.

[1.26.2005] Quantum relays for long distance quantum cryptography

2005-01-26T03:32:00.000Z

Journal of Modern Optics
Issue: Volume 52, Number 5 / March 20, 2005
Pages: 735 - 753

URL: JMO52.0735, 2005
Linking Options

DOI: 10.1080/09500340412331283633
Quantum relays for long distance quantum cryptography
Daniel Collins , Nicolas Gisin , Hugues De Riedmatten
A1 Group of Applied Physics University of Geneva 20 rue de l'Ecole-de-Médecine CH-1211 Geneva 4 Switzerland
Abstract:
Quantum cryptography is on the verge of commercial application. One of its greatest limitations is over long distance--secret key rates are low and the longest fibre over which any key has been exchanged is currently 100km. We investigate the quantum relay, which can increase the maximum distance at which quantum cryptography is possible. The relay splits the channel into sections and sends a different photon across each section, increasing the signal-to-noise ratio. The photons are linked as in teleportation, with entangled photon pairs and Bell measurements. We show that such a scheme could allow cryptography over hundreds of kilometres with today's detectors. It could not, however, improve the rate of key exchange over distances where the standard single section scheme already works. We also show that reverse key reconciliation, previously used in continuous variable quantum cryptography, gives a secure key over longer distances than forward key reconciliation.

[1.26.2005] Faked states attack on quantum cryptosystems

2005-01-26T03:25:00.000Z

Journal of Modern Optics
Volume 52, Number 5 / March 20, 2005
Pages:
691 - 705

URL: JMO52.0691,2005
DOI: 10.1080/09500340410001730986

Faked states attack on quantum cryptosystems
Vadim Makarov and Dag R. Hjelme
A1 Department of Electronics and Telecommunications Norwegian University of Science and Technology (NTNU) NO-7491 Trondheim Norway
Abstract:
A new type of attack on quantum cryptography systems is proposed. In this attack, Eve utilizes various optical imperfections in Bob's scheme and constructs light pulses so that Bob does not distinguish his detection results from normal, whereas they give Bob the basis and bit value chosen at Eve's discretion. Applying this attack to systems with passive basis choice on Bob's side is considered. Also, a general workflow of breaking into a running quantum cryptolink using this or Trojan horse attack is discussed.

[1/6/2005]Auto-compensating differential phase shift quantum key distribution

2005-01-07T05:12:00.000Z

Authors: Xiaohong Han, Guang Wu, Chunyuan Zhou, Heping Zeng

We propose an auto-compensating differential phase shift scheme for quantum key distribution with a high key-creation efficiency, which skillfully makes use of automatic alignment of the photon polarization states in optical fiber with modified Michelson interferometers composed of unequal arms with Faraday mirrors at the ends. The Faraday-mirrors-based Michelson interferometers not only function as pulse splitters, but also enable inherent compensation of polarization mode dispersion in the optic-fiber paths at both Alice's and Bob's sites. The sequential pulses encoded by differential phase shifts pass through the quantum channel with the same polarization states, resulting in a stable key distribution immune to the polarization mode dispersion in the quantum channel. Such a system features perfect stability and higher key creation efficiency over traditional schemes.

http://arxiv.org/abs/quant-ph/0501025

Secure Coherent-state Quantum Key Distribution Protocols with Efficient Reconciliation

2004-10-07T17:23:00.000+01:00

Authors: G. Van Assche, S. Iblisdir, N. J. Cerf
Comments: REVTeX, 11 pages, 2 figures

We study the equivalence between a realistic quantum key distribution protocol using coherent states and homodyne detection and a formal entanglement purification protocol. Maximally-entangled qubit pairs that one can extract in the formal protocol correspond to secret key bits in the realistic protocol. More specifically, we define a qubit encoding scheme that allows the formal protocol to produce more than one entangled qubit pair per coherent state, or equivalently for the realistic protocol, more than one secret key bit. The entanglement parameters are estimated using quantum tomography. We analyze the properties of the encoding scheme and investigate its application to the important case of the attenuation channel.
http://uk.arxiv.org/abs/quant-ph/0410031

Practical quantum key distribution with polarization entangled photons

2004-08-20T10:25:00.000+01:00

We present an entangled-state quantum cryptography system that operated for the first time in a real-world application scenario. The full key generation protocol was performed in real-time between two distributed embedded hardware devices, which were connected by 1.45 km of optical fiber, installed for this experiment in the Vienna sewage system. The generated quantum key was immediately handed over and used by a secure communication application.
(http://www.opticsexpress.org/abstract.cfm?URI=OPEX-12-16-3865)

Stability of Phase-modulated Quantum Key Distribution System

2004-08-06T23:57:00.000+01:00

Title: Stability of Phase-modulated Quantum Key Distribution System
Authors: Zheng-Fu Han, Xiao-Fan Mo, You-Zhen Gui, Guang-Can Guo
Comments: 9 pages, 3 figues\Phase drift and random fluctuation of interference visibility in doubleunbalanced M-Z QKD system are observed and distinguished. It has been foundthat the interference visibilities are influenced deeply by the disturbance oftransmission fiber. Theory analysis shows that the fluctuation is derived fromthe envioronmental disturbance on polarization characteristic of fiber,especially including transmission fiber. Finally, stability conditions ofone-way anti-disturbed M-Z QKD system are given out, which provides atheoretical guide in pragmatic anti-disturbed QKD.\ ( http://arXiv.org/abs/quant-ph/0408031 , 372kb)

[20040720] CV attack 2

2004-07-20T10:18:00.000+01:00

Title Security bounds for continuous variables quantum key distribution
Authors: Miguel Navascues, Antonio Acin
Comments: See also F. Grosshans, quant-ph/0407148

Security bounds for key distribution protocols using coherent and squeezed states and homodyne measurements are presented. These bounds refer to (i) general attacks and (ii) collective attacks where Eve interacts individually with the sent states, but delays her measurement until the end of the reconciliation process. For the case of a lossy line and coherent states, it is first proven that a secure key distribution is possible up to 1.9 dB of losses. For the second scenario, the security bounds are the same as for the completely incoherent attack.
(http://arxiv.org/abs/quant-ph/0407149)

[20040720] CV attack 1

2004-07-20T10:08:00.000+01:00

Title: Collective attacks and unconditional security in continuous variable quantum key distribution
Authors: Frederic Grosshans

We present here an information theoretic study of Gaussian collective attacks on the continuous variable key distribution protocols based on Gaussian modulation of coherent states. These attacks, overlooked in previous security studies, give a finite advantage to the eavesdropper in the experimentally relevant lossy channel, but are not powerful enough to reduce the range of the reverse reconciliation protocols. Secret key rates are given for the ideal case where Bob performs optimal collective measurements, as well as for the realistic cases where he performs homodyne or heterodyne measurements. We also apply the generic security proof of Christiandl et. al. [quant-ph/0402131] to obtain unconditionally secure rates for these protocols.
(http://arxiv.org/abs/quant-ph/0407148)

Key distribution & Attack

2004-07-19T23:40:00.000+01:00

Title: Cryptanalysis of a Practical Quantum Key Distribution With Polarization-Entangled Photons
Authors: Thomas Beth and Joern Mueller-Quade and Rainer Steinwandt
Comments: 6 pages\\
Recently, a quantum key exchange protocol has been described, which served asbasis for securing an actual bank transaction by means of quantum cryptography[quant-ph/0404115]. Here we show, that the authentication scheme applied isinsecure in the sense that an attacker can provoke a situation where initiatorand responder of a key exchange end up with different keys. Moreover, it mayhappen that an attacker can decrypt a part of the plaintext protected with thederived encryption key.\\
( http://arXiv.org/abs/quant-ph/0407130 , 5kb)
------------------------------------------------------------------------------\Title: A Novel Protocol-Authentication Algorithm Ruling Out a Man-in-the-Middle Attack in Quantum Cryptography
Authors: M. Peev, M. N\"olle, O. Maurhardt, T. Lor\"unser, M. Suda, A. Poppe, R. Ursin, A. Fedrizzi and A. Zeilinger
Comments: 4 pages, submitted to the International Journal of Quantum Information, Proceedings of the meeting "Foundations of Quantum Information", Camerino, April 2004\\

In this work we review the security vulnerability of Quantum Cryptographywith respect to "man-in-the-middle attacks" and the standard authenticationmethods applied to counteract these attacks. We further propose a modifiedauthentication algorithm which features higher efficiency with respect toconsumption of mutual secret bits.\\
( http://arXiv.org/abs/quant-ph/0407131 , 8kb)

Security of Y-00 and similar quantum cryptographic protocols

2004-07-12T10:50:00.000+01:00

Authors: Horace P. Yuen, Prem Kumar and Eric Corndorf
Comments: Submitted to Physics Letters A, July 2004
\It is claimed in Phys. Lett. A by T. Nishioka et. al.
327 (2004) 28-32, that the security of Y-00 is equivalent
to that of a classical stream cipher. In this paper it is
shown that the claim is false. The erroneous assertions made
in that paper are delineated. The security of Y-00 type
protocols in both key generation and direct encryption
are clarified.
\\ ( http://arXiv.org/abs/quant-ph/0407067, 45kb)

Experimental quantum key distribution over highly noisy channels

2004-07-06T09:32:00.000+01:00

Authors: L.P. Lamoureux, E. Brainis, N. Cerf, Ph. Emplit,
M. Haelterman, S. Massar
Comments: 4 pages, 2 figures
\ Error filtration is a method for encoding the quantum
state of a single particle into a higher dimensional
Hilbert space in such a way that it becomes less sensitive
to phase noise. We experimentally demonstrate this method by
distributing a secret key over an optical fiber whose noise
level otherwise precludes secure quantum key distribution.
By filtering out the phase noise, a bit error rate of 15.3%
+/- 0.1%, which is beyond the security limit, can be reduced
to 10.6% +/- 0.1%, thereby guaranteeing the cryptographic security.
\\ ( http://arXiv.org/abs/quant-ph/0407031 , 40kb)

Common origin of no-cloning and no-deleting principles - Conservation of Information

2004-07-06T09:22:00.000+01:00

Authors: Michal Horodecki, Ryszard Horodecki, Aditi Sen De, Ujjwal Sen
Comments: This paper is dedicated to Asher Peres on the occasion of
his seventieth birthday\

We discuss the role of the notion of information in the
description of physical reality. We consider theories
for which the dynamics is linear with respect to stochastic mixing.
We point out that the no-cloning and no-deleting principles emerge
in any such theory, if law of conservation of information is
valid, and two copies contain more information than one copy.
We then describe the quantum case from this point of view.
\\ (
http://arXiv.org/abs/quant-ph/0407038, 9kb)

Error Filtration and Entanglement Purification for Quantum Communication

2004-07-05T09:43:00.000+01:00

Authors: N. Gisin, N. Linden, S. Massar, S. Popescu
Comments: 23 pages (latex) and 4 postscript figures
\ The key realisation which lead to the emergence of
the new field of quantum information processing is that
quantum mechanics, the theory that describes
microscopic particles, allows the processing of information
in fundamentally new ways. But just as in classical information
processing, errors occur in quantum information processing,
and these have to be corrected. A fundamental breakthrough
was the realisation that quantum error correction is in fact
possible. However most work so far has not been concerned
with technological feasibility, but rather with proving
that quantum error correction is possible in principle.
Here we describe a method for filtering out errors and
entanglement purification which is particularly suitable
for quantum communication. Our method is conceptually new,
and, crucially, it is easy to implement in a wide variety
of physical systems with present day technology and
should therefore be of wide applicability.
\\
(
http://arXiv.org/abs/quant-ph/0407021 , 79kb)

The method for our communication

2004-06-28T00:06:00.000+01:00

i) latex2html
ii) WikiWik.....

Please post the link for the utilitise....

First article

2004-06-27T23:48:00.000+01:00

This is test article which is for testing this blog page.
I wish that we can use this page for the progress of web-based-communication which is for the exchange of the research ideas.