WO2008140291A2 - Rendu déterministe pour cryptographie quantique pratique - Google Patents

Rendu déterministe pour cryptographie quantique pratique Download PDF

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Publication number
WO2008140291A2
WO2008140291A2 PCT/MY2008/000039 MY2008000039W WO2008140291A2 WO 2008140291 A2 WO2008140291 A2 WO 2008140291A2 MY 2008000039 W MY2008000039 W MY 2008000039W WO 2008140291 A2 WO2008140291 A2 WO 2008140291A2
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WO
WIPO (PCT)
Prior art keywords
bits
deterministic
basis
bit
practical
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/MY2008/000039
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English (en)
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WO2008140291A3 (fr
Inventor
Mohamed Ridza Wahidin
Jesni Bin Shamsul Shaari
Marco Lucamarni
Stefano Mancini
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mimos Bhd
International Islamic University Malaysia
Original Assignee
Mimos Bhd
International Islamic University Malaysia
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Filing date
Publication date
Application filed by Mimos Bhd, International Islamic University Malaysia filed Critical Mimos Bhd
Publication of WO2008140291A2 publication Critical patent/WO2008140291A2/fr
Publication of WO2008140291A3 publication Critical patent/WO2008140291A3/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
    • H04L9/08—Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords
    • H04L9/0816—Key establishment, i.e. cryptographic processes or cryptographic protocols whereby a shared secret becomes available to two or more parties, for subsequent use
    • H04L9/0852—Quantum cryptography
    • H04L9/0858—Details about key distillation or coding, e.g. reconciliation, error correction, privacy amplification, polarisation coding or phase coding

Definitions

  • the present invention relates to a quantum key distribution (QKD) protocol in order to make it deterministic.
  • QKD quantum key distribution
  • the present invention more particularly relates to a method and system for deterministic quantum key distribution for rendering practical quantum cryptography.
  • QKD quantum key distribution
  • the basic reconciliation implies the average waste of partial of the total quantum resources used for the quantum communication.
  • the basis reconciliation's intrinsic randomness it is not possible to affirm that the final key is distributed from one user to another, but rather that it is generated during the protocol itself in a random way.
  • the usual BB84 is not deterministic. This feature is not necessarily a disadvantage, but it prevents even in principle the possibility of a quantum "direct communication' with the BB84.
  • the present invention relates to a deterministic rendering for practical quantum cryptography for conveying information from one site to another site with security wherein the steps for dete ⁇ ninisting BB84 comprises of:
  • U2 selects a subset of 2N bits that will serve as a check on User 3's
  • the present invention also relates to a deterministic rendering for practical quantum cryptography for a practical deterministic BB84, wherein the steps comprises of:
  • U2 selects a subset of 2N bits of d and 2N bits of b that will serve as a check on U3's interference, and tells Ul the addresses of the selected bits and wherein Ul selects the same addresses from the strings B and D.
  • U2 and Ul announce on the classical channel the v dues of the selected 2N pairs of bits from b and
  • U2 1 ansmits the information about the basis without waiting for Ul's receipt and wherein Ul does not send the receipt in the very moment Ul receives the photon.
  • Figure 1 shows a diagram of a possible Implementation of BB84'
  • Figure 2 shows 4 different graphs shoei inngg a secure rate of BB84' and BB84 optimized for distances between U2 and Ul for 2, ⁇ , 8 and 16 KM.
  • U2 chooses a random (4 + ⁇ c + ⁇ m ) N-bit string d (data string).
  • the factor ⁇ c accounts for the losses of the channel while ⁇ m accounts for the losses of Ul's storage memory.
  • U2 chooses a random (4 + ⁇ c + ⁇ m ) N-bit string b (basis string).
  • U2 encodes each bit of d on the qubits as ⁇ K)>, ll> ⁇ if the corresponding bit of b is 0 (Z basis) or ⁇ l+>, l-> ⁇ if the corresponding bit of b is 1 (X basis).
  • U2 sends the resulting states to Ul. (c) Storage.
  • U2 selects a subset of 2N bits that will servje as a check on User 3's (U3) interference, and tells Ul which bits U2 selected.
  • step c, e and d of the above protocol makes it deterministic, because they let Ul always measure in the right basis. T us would enable the possibility of a direct communication in case of a noiseless and loss less channel between the users.
  • the coefficient in front of the final number of distilled bits is 2 for BB84' while in the BB84 it is 1. This is due to the determinism of the new protocc 1, and entails an increase of the secure-bit-rate, at least on small distances between U2 ind Ul. For long distances the loss-rate becomes important eventually suppressing the advantage given by the determinism.
  • the minimum storage time for the deterministic BB84 with a receipt's transmission is 2T.
  • T is the time for a signal to cover the distance between U2 and Ul: one T is to let Ul 's receipt reach U2, and one T is to let U2 transmit the basis to Ul (we assume for simplicity that U2 and Ul use the same channel, hence the two times are equal in both directions).
  • U2 and Ul measure the time T that an intense light pulse employs to cover the distance between them. Then they use the (authenticated or unjammable) classical channel to declare the measured time T and to established the value of a positive security parameter, ⁇ , used later for security analysis.
  • T 1 U2 acquires the (4 + ⁇ c + ⁇ m ) N basis bits bj, and labels them as Bi.
  • This step is very similar to receiving a normal telephone call.
  • Ul records both the values of the B,'s and their times of arrival T 1 -.
  • BB84 removes the problem of Ul's receipt, relying much more on the classical communication.
  • the main ingredient is a kind of "post-selected" receipt by Ul.
  • U2 transmits the information about the basis without waiting for Ul's receipt. Ul does not send the receipt in the very moment Ul receives the photon. Yet Ul final measurement will reveal whether the photon was there at the expected time. Thus the main problem of a QND measurement is removed at the roots.
  • BB84 is entirely equivalent to the first protocol we described in this work, which, in turn, has been shown to be secure and equivalent to the original BB84.
  • the security analysis as in the present invention is aimed at showing the security of BB84" against attacks based on the potential weakness created by the Ul's receipt removal. It can also be seen as a new security argument in the frame of "sequential" QKD protocols. For the moment it is consider Ul's measuring apparatus is ideal, and we do not include in the proof the experimental parameters ⁇ , ⁇ ' and ⁇ .
  • the attackable point of our protocol is the lack of a qubit receipt from Ul to U2.
  • the risk is that U3 uses the disclosed basis bit to measure the qubit without perturbing it. Any other kind of eavesdropping is tantamount to U3 attacking a qubit just as she would do against a normal BB84 system. To do that U3 can either delay the qubit until the basis is disclosed or delay both the qubit and the basis. Any delay of the basis bits is detected during the check of the arrival times performed at point of (i), thus ruling out the latter strategy.
  • the former attack is instead slightly more subtle and is analyzed below.
  • U3 can not alter the values of the bases decided by U2 in a kind of v man-in-the-middle' attack, because they are declared at point of (i).
  • the crucial quantity is the parameter ⁇ : how big should it be to maintain the security of the protocol?
  • the quantity ⁇ represents a kind of experimental error in determining the exact time of arrival of the photons at Ul's site.
  • e is the time window of Ul 1 S "gated mode" detectors (Le. detectors which are open only when a photon is expected to be there); otherwise, when the photons are generated through the spontaneous parametric down conversion, ⁇ is the time window of the coincidence counts. In both cases typical values of e are less than 10 ns.
  • the quantum channel is a pulsed attenuated laser at the wavelength ⁇ f 1500 ran
  • the trigger is a pulsed bright laser at the wavelength of 1300 nm, which is used to synchronize the whole optical acquisition
  • the classical channel is the Internet, which is employed to transfer the information about the bases and about error correction and privacy amplification.
  • the start pulse from the computer drives the two laser sources (Ll @ 1500 nm, the quantum signal, and L2@1300 nm, the trigger) and the phase modulator which encodes the information in the relative pha ⁇ of the pulses generated by Ll and split in two time bins by U2's interferometer.
  • the random number generator (RNG) is drawn as detached fro n the computer for simplicity.
  • the phase encoded on the pulses is determined by the suim of the values of the basis (0 or ⁇ /2) and that of the state (0 or ⁇ ).
  • the important feature is that the basis is also written on the bright pulse @ 1300 nm, which now has a twofold role: time reference for U2 and carrier of the basis information.
  • a delay line represented by a number of fiber loops, of length L • ⁇ ⁇ .
  • L TcM
  • ⁇ ⁇ c/n, with n the refractive index of the fiber and c the speed of light in vacuum.
  • the WDM selects the bright pulse, which is directed at a PIN photodiode detector.
  • This acts as a trigger for the gate of the avalanche photodiode detectors APDl and APD2.
  • the value read by the detector acts as an input to the electro-optical phase modulator represented by ⁇ B in the figure, thus allowing the deterministic measurement by Ul.
  • the path followed by the quantum carrier photon from laser Ll is the same. The only difference is the delay on Ul's site, which is equal to the one at U2's. This delay represents the simplest quantum memory and allows Ul to wait for the information about the basis before Ul's final measurement, making it deterministic. So in the whole, with respect to the usual BB84, no additional material other than some electronics is required for the implementation of BB84".
  • P ⁇ is the probability Ul gets a dark count in bis detectors
  • P ⁇ " 1 is the probability that Ul's detector fires because of a photon emitted by U2's source. This probability decreases with the distance between the users according to the formula:-
  • ⁇ B is the quantum efficiency of Ul's detectors
  • ⁇ is the average number of photons per pulse
  • ⁇ T is the transmission probability of the channel, given by:
  • ⁇ T i ⁇ - ( ⁇ t+ ⁇ )/10 (6)
  • ⁇ is the absorption coefficient of the fiber
  • L 0 is the loss rate at receiver's station
  • L is the distance between the users, as shown in Figure 1.
  • Equation. (3) ⁇ is defined as:
  • the rate of distilled secure bits is one of the figures of merit of a QKD setup, and it is not a trivial task to increase it.
  • the rate of transmission in any fiber-based setup is currently limited by the low efficiency of detectors, and in particular by their dead times, which are of the order of microseconds for a standard APD detector. This is a technological limitation that can be surpassed only by improving the detection mechanism.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Theoretical Computer Science (AREA)
  • Computer Security & Cryptography (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Optical Communication System (AREA)

Abstract

La présente invention concerne un protocole de distribution de clé quantique (QDK) permettant d'obtenir un rendu déterministe. La présente invention concerne plus particulièrement un procédé et un système de distribution de clé quantique déterministe pour rendu de cryptographie quantique pratique.
PCT/MY2008/000039 2007-05-11 2008-05-09 Rendu déterministe pour cryptographie quantique pratique Ceased WO2008140291A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
MYPI20070735 2007-05-11
MYPI20070735 2007-05-11

Publications (2)

Publication Number Publication Date
WO2008140291A2 true WO2008140291A2 (fr) 2008-11-20
WO2008140291A3 WO2008140291A3 (fr) 2009-03-12

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2503045A (en) * 2012-06-13 2013-12-18 Toshiba Res Europ Ltd Quantum cryptography system with error correction and privacy amplification

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DK0923828T3 (da) * 1996-09-05 2004-05-24 Swisscom Ag Kvantekryptografiindretning og fremgangsmåde
WO2004015545A2 (fr) * 2002-08-10 2004-02-19 Routt Thomas J Procedes d'emission de donnees par des interfaces quantiques et portes quantiques utilisant ces procedes
JP2005117511A (ja) * 2003-10-10 2005-04-28 Nec Corp 量子暗号通信システム及びそれに用いる量子暗号鍵配布方法
JP2005268958A (ja) * 2004-03-16 2005-09-29 Nippon Telegr & Teleph Corp <Ntt> 量子暗号通信装置

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2503045A (en) * 2012-06-13 2013-12-18 Toshiba Res Europ Ltd Quantum cryptography system with error correction and privacy amplification
GB2503045B (en) * 2012-06-13 2014-05-28 Toshiba Res Europ Ltd A quantum communication method and system

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WO2008140291A3 (fr) 2009-03-12

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