WO2002039639A2 - Procede et systeme de transmission par cryptographie quantique - Google Patents
Procede et systeme de transmission par cryptographie quantique Download PDFInfo
- Publication number
- WO2002039639A2 WO2002039639A2 PCT/FR2001/003500 FR0103500W WO0239639A2 WO 2002039639 A2 WO2002039639 A2 WO 2002039639A2 FR 0103500 W FR0103500 W FR 0103500W WO 0239639 A2 WO0239639 A2 WO 0239639A2
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- WO
- WIPO (PCT)
- Prior art keywords
- time
- pulses
- particle
- particles
- value
- Prior art date
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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 invention relates to the field of cryptography.
- a message can only be read by its recipient.
- a key is used to encrypt the message. Only the owner of the key is able to read the message on reception.
- the encryption key must therefore be transmitted by the sender to the recipient of the encrypted message. This transmission is carried out such that only the recipient of the encrypted message receives this encryption key. Interception by a third party of the encryption key is detected by the sender or the recipient. Thus, the encryption key or the elements of the key detected
- An example of the principle of transmitting encryption keys is that of quantum cryptography. It consists of using physical properties to ensure the integrity of a received encryption key.
- the encryption key is made up of a sequence of bits. In general, each bit is associated with a polarization state of a photon. Then, the polarized coded light flux is attenuated. The probability of detecting two photons associated with the same bit is, therefore, negligible.
- the transmitter can encode the encryption key in two non-orthogonal states (a given polarization state and a 45 ° state). On this subject, Bennett writes the article "Quantum Cryptography using any two Nonorthogonal states" in Physics Review letters 68 in 1992. On reception, the detection states are chosen from a two-state base. These two detection states are orthogonal respectively to each of the states of the base used by the transmitter. During transmission, the choice of emission and detection states is made independently of each other.
- the probability of detection is zero.
- the measurement result is certain, there is no ambiguity.
- the probability of detecting the photon is 0.5. If the photon is detected, it is certain that the state of the emitter is 45 ° from the state of the receiver. There is no ambiguity. Whatever the polarization configuration, there is always a possibility of not detecting the photon. This non-detection of the photon makes it ambiguous to deduce the choice of polarization of the transmitter from knowledge of the state of the receiver. It is this ambiguity about polarization that is used in quantum cryptography. A non-recipient will not be able to reproduce the message because they will not be able to avoid the loss of information.
- This quantum cryptography is said by polarization ambiguity due to the use of polarization states of photons. It poses a number of problems. They are linked to the coding of the encryption key on the polarization states of the photons of a light flux.
- the transmission faces a problem of polarization distortion. For example, during transmission by optical fibers, this requires devices which are complex to implement and of high cost. For example,
- the present invention proposes an alternative: quantum cryptography by ambiguity in the time domain. Its implementation is simpler because it is protected among other things from transmission problems by optical fibers. Indeed, two photons emitted successively with a time difference ⁇ t will be received in the order of emission with the same time difference ⁇ t, regardless of the transmission medium.
- the subject of the invention is a method of coding digital data intended for transmission by particle flow such that the probability of emission of two particles per period is negligible, characterized in that it comprises the transformation of the sequence of K bits of digital data in a train of K pulses of flow of particles of temporal width ⁇ T whose periodicity Tb is predetermined knowing that each of the K pulses is shifted or not temporally such that the k ⁇ e m e j m p U
- FIG. 1 the representation of the value of a bit transmitted in the form of a pulse according to the invention
- FIG. 5 a second embodiment of the second variant of the coder 1 according to the invention.
- FIG. 6 the mechanical chopper disc of the third and fourth embodiments of the second variant of the encoder 1 according to the invention
- FIG. 7 (a) a third embodiment of the second variant of the coder 1 according to the invention.
- FIG. 10 a first exemplary embodiment of the transmission system by quantum cryptography according to the invention, - Figure 11 (a) and 11 (b), two variants of the decoder according to the invention,
- the principle of the present invention resides in the reproduction of the state of the art polarization ambiguity diagram in the time domain.
- the information is coded in pulses of temporal width ⁇ T as shown in FIG. 1.
- These pulses can, for example, be light pulses. They can generally be pulses of particle fluxes (photons, electrons, positrons ).
- Each time period of duration Tb is associated with a bit of digital data constituting the information to be coded.
- One of the pulses is associated with the bit of value "0" (the one shifted by tO relative to the initial instant of the period of duration Tb), the other with the bit with value "1" (the one shifted by t1) .
- the duration Tb is such that it verifies the following relation Tb> ⁇ T + lt1-t0l.
- tO and t1 are such that 0 ⁇ t0, t1 ⁇ Tb - ⁇ T and 0 ⁇ It1 -toi ⁇ T.
- the receiver detects a photon during the recovery period, it cannot know what type of pulse it comes from, so what is the value "0" or "1" of the bit that was sent. In order to detect the value of the bit unambiguously, only the photons received in two time windows given in FIG. 2 are observed. One of the windows allows you to observe the first half of the first pulse, and the other the second half of the second pulse. Therefore, the photons arriving at the receiver during the overlap time interval ⁇ t are not observed. More explicitly, the decoding comprises: • the observation of the particle flow received over one or two time windows for each of the periods of duration Tb of reception of a bit,
- the first observation time window begins at time tO (included) and ends at time t1 (excluded)
- the second observation window starts, if necessary, at time t1 + ⁇ t (excluded) and ends at time t1 + T (included) or vice versa
- the first observation time window begins at time t1 (included) and ends at time tO (excluded)
- the second observation window starts, if necessary, at time tO + ⁇ t (excluded) and ends at time tO + T (included) or vice versa
- the bits are sent according to the format of figure 1 and the observation windows of the receiver are given by figure 2.
- the particle flow pulses carrying the information to be transmitted in the form of a time offset are, for example:
- the various coders 1 and decoders 3 envisaged in FIGS. 3 to 12 are given by way of example. They illustrate coding on a light beam. More generally, any type of particle flux (photons, electrons, positrons, etc.) can be considered.
- the encoder 1 comprises at least one source with coded pulses 11 +3 . It directly produces particle flux pulses of temporal width ⁇ T and of periodicity Tb. The pulses from this source are further shifted by t0 or t1 according to the value of the information bits to be coded.
- the values of the time offsets tO and t1 are such that 0 ⁇ tO.tl ⁇ Tb - ⁇ T and 0 ⁇ It1-t0l ⁇ T.
- FIG. 3 shows a second variant of the encoder 1 using a modulator 131.
- the modulator 131 is electro-optical or acousto-optical ...
- the encoder 1 comprises a pulse source 11 +2 .
- This source 11 + 2 delivers a flow of particles in the form of a train of pulses of temporal width ⁇ T and of periodicity Tb.
- the 11 +2 pulse source is, for example, a mode-locked laser. Mode-locked lasers produce pulse trains separated by a constant time interval equal to the round trip time in the laser cavity. It is difficult to act on the laser in order to be able to produce the desired time offsets according to the bits to be coded.
- the retarder 13 causes the pulses to traverse or not a delay line according to the desired offset determined by the bits to be coded.
- a retarder 13 can, for example, be produced using a modulator 131 which makes it possible to switch the polarization between two directions specific to the polarizing prisms 132s and 132R placed downstream.
- the polarizing prism 132s then guides the pulses according to their polarizations towards a first or a second path.
- the second polarizing prism 132R brings them back to the output of the retarder 13.
- the path traveled is more or less long. For example, if the impulse is not offset, it follows a direct path and if it is offset, it follows an elongated path.
- the first embodiment of the third variant of the encoder 1 presented by FIG. 3 (a) is simple.
- the beam from the laser 11 passes through a modulator 121.
- the modulator 121 has two operating modes: an active mode and an inactive mode. It can be electro-optical, acousto-optical, etc.
- the modulator 121 receives a control signal which has two states. One of the states corresponding to the inactive mode and the other state to the active mode.
- Figure 3 (b) shows the control voltage of an electro-optical modulator 121. Its shape is adapted to the creation of pulses of temporal width ⁇ T at a rate Tb with a time offset tO or t1 according to the value "0" or "1" of the bits.
- the modulator 121 When the control voltage reaches a threshold value V ⁇ , the modulator 121 is active. An active modulator 121 switches the polarization of the light beam passing through it by 90 °. A polarizer 122 is placed downstream of the modulator 121. The polarizer 122 switches off the beam when the modulator 121 is not activated. In fact, the polarizer 122 only lets the beam pass when its polarization corresponds to that obtained at the output of the active modulator 121. Therefore, at rest, no beam is transmitted by the 12 + 3 system.
- This first embodiment of the third variant of the coder 1 therefore comprises a source 11 of particles in continuous flow followed by a coded pulse cutter 12 +3 having at least one coded pulse recorder 121 receiving the continuous flow , and a switch 122 allowing transmission only during the recorded pulse.
- Another technique consists in using a mechanical chopper 123 which cuts pulses of temporal width ⁇ T given at the desired rate Tb on a continuous flow of particles.
- Figure 5 shows a second embodiment of the third variant of the encoder 1. It uses a mechanical chopper whose disc 123 ⁇ has only one opening.
- a phase control device 124 generates a voltage (VCO) for controlling the speed of rotation of the disc 123 ⁇ .
- VCO voltage
- the variation of the control voltage makes it possible to more or less phase-shift the rotation of the disc and, therefore, to temporally offset by time t0 or t1 the creation of a pulse in the beam coming from the laser 11.
- the use of a disc 123 2 with two openings like the one presented in FIG. 6 eliminates the need to control the phase of rotation of the disc. So that the pulses are of the same shape and of the same duration T, the two openings are of identical shape (triangles, squares, rectangles ). In addition, they are diametrically opposed and offset by 1/2 of an opening. The two pulses created are thus offset by half a width.
- the advantage is to ensure the offset of ⁇ T / 2 regardless of the spectral width of rotation of the disc. For an offset other than ⁇ T / 2, the offset is no longer 1/2 opening but adapted to the desired time offset.
- the two pulses are created on two separate beams because of orthogonal polarizations, as shown in Figures 7 (a) and 8.
- the beam from the laser 11 is separated into two beams.
- the polarizations of these two beams are orthogonal. This separation is carried out, for example, using a 122 M polarizing prism.
- the disc 123 2 is placed such that one of the beams passes directly through one of the openings.
- the other beam is guided towards the other opening by, for example, a 125 "mirror.
- One of the beams then comprises pulses at times t1 and the other beam of pulses at times tO. For coding information, it is then necessary to choose one or the other of the two impulses.
- the third embodiment of the third variant of the encoder 1 presented by FIG. 7 (a) proposes a first device for choosing pulses.
- the two beams are recombined after their passage in the disc 123 2 .
- a 122v repolarizer cube performs this recombination. he is placed on the path of one of the beams.
- the other beam is guided towards the repolarizing cube 122 v using, for example, a mirror 125 '.
- the recombined beam presents the two types of pulses t0 and t1 each on a given polarization as shown in Figure 7 (b).
- the device of choice is placed on the light beam resulting from the recombination.
- the modulator 121 includes, for example, a modulator 121 which is activated or not depending on the chosen pulse.
- the modulator 121 places the selected pulses corresponding to the data to be coded on a given polarization. Then, the device of choice lets through only the polarization containing the pulses chosen using a polarizer 122.
- the selection device presented by the fourth embodiment of the third variant of the encoder 1 in FIG. 8 is produced according to another technique. It is an optical referral technique. It uses, for example, a Mach-Zender i interferometer set to zero path difference.
- the interferometer has two input and output channels as shown in Figures 9 (a) and 9 (b).
- one or other of the input channels is connected to one or other of the exit routes.
- This phase shift can be easily achieved by mounting one of the mirrors 125j "'on a piezoelectric shim 127
- the embodiments of the third variant of the encoder 1 in FIGS. 7 and 8 show a coded pulse cutter 12 + 3 which has a given structure.
- the coded pulse cutter 12 +3 comprises at least one particle stream separator 122 on two channels. 123 proper makes it possible to cut out pulses offset by tO on the first channel and by t1 on the second channel from the flow of particles.
- a device (121 + 122 or i) makes it possible to choose the pulse offset by tO or of t1 according to the value "0" or "1" of the bit to code over this period.
- the fourth variant of encoder 1 is not illustrated. It has a source providing a continuous flow of particles (single mode laser ). In the continuous flow, pulses of temporal width ⁇ T are cut at a rate Tb. They are produced by a pulse cutter 12 generating pulses either not offset, or all offset by t (0 ⁇ t ⁇ Tb - ⁇ T).
- the pulse cutter 12 can be of structure, for example, similar to that of the coded pulse cutters 12 +3 described above.
- the pulses are then offset or not by a retarder 13 (for example similar to that of the second variant of the encoder 1).
- the pulses at the output of the self-timer 13 then carries the information to be transmitted according to, for example, the diagram in FIG. 1.
- an encoder 1 comprising, for example, a cutter d 'pulses coded 12 +3 on the flow of particles coming from a continuous source 11, they must be attenuated.
- the probability that the decoder 3 represented in FIG. 10 detects two photons in the same pulse must be negligible. It is this principle that brings the quantum dimension of cryptography.
- the attenuator 2 is placed after the encoder 1 in the transmitter. It comprises a half-wave plate 21 followed by a polarizer 22 which produces two beams: a "key" attenuated beam and an annex beam. The intense beam exiting through the annex channel can also be transmitted to the receiver.
- the "sync" signal is transmitted either directly in optical form, or in the form of a microwave signal ...
- a first variant of the decoder 3 presented in FIG. 11 (a) comprises a photon counter 31 ′ activated only during the observation windows represented in FIG. 2. Depending on the detection of a photon of the "key” quantum signal by the photon counter 31 'in one or other of the observation windows, the decoder 3 decides that a bit of value "0" or "1" has been sent. If the photon counter 31 ′ does not detect a photon in one or other of the observation windows, the decoder 3 decides that there is no reception. It cannot determine whether this non-reception is due to poor quality transmission or interception by a third person.
- a second variant of the decoder 3 proposed by FIG. 11 (b) can be used.
- the laser 11 used to produce such pulses can be, for example, a mode-locked laser.
- the photons of the received "key" quantum signal are filtered by a filter of spectral width ⁇ v.
- the photons of spectral width ⁇ v are observed by the photon counter 31 'activated on the observation windows presented in FIG. 2.
- the photons reflected by the filter ⁇ v are also counted by a photon counter 31 ".
- the comparator 32 checks if the number N ⁇ f of reflected photons is greater than much greater than the numbers N ⁇ v of photons observed in the observation windows If this is the case, the decoder 3 decides that the information transmitted has been intercepted by a third person Otherwise, depending on whether the photon counter 31 ′ detects a photon in one or other of the observation windows, the decoder 3 decides that a bit of value "0" or "1" has been sent. , if the photon counter 31 ′ does not detect a photon in one or other of the observation windows, the decoder 3 decides that there is non-reception. It cannot determine whether this non-reception is due poor transmission or interception by a third party.
- the durations of the pulses can be, then, between 10 ps and 100 fs. These values are much lower than the response times of certain existing photon counters (typically 1 ns).
- the photon counter (31, 31 ') cannot distinguish an offset pulse from a non-offset pulse, or an offset pulse from t0 from that offset from t1.
- This function can then be performed using, for example, an optical gate (not shown in the figures) upstream of the photon counter (31, 31 '). This door is electrically controlled. It must be fast enough to make it possible to produce detection gates of sufficiently short duration corresponding to the observation windows of FIG. 2 if the photon counter (31, 31 ') has too long a response time.
- the decoder 3 presented in FIGS. 11 (a) and 11 (b) therefore comprises at least one particle counter 31 ′ either activated on the observation windows of FIG. 2, or placed downstream of a door producing particle detection doors corresponding to these windows. If the pulses emitted by the transmitter are in a minimal state, the decoder read
- ⁇ v may, in addition, include a filter of spectral width ⁇ v upstream of the particle counter 31 '. It can also include a particle counter 31 "on the flux reflected by the filter ⁇ v and a comparator 32 receiving the number of particles detected by the particle counters 31 'and 31" capable of detecting the interception of transmission by a third.
- FIG. 12 shows a second embodiment of the transmission system by quantum cryptography with time coding according to the invention.
- a pulse source 11 +2 delivers the flow of particles in the form of a train of pulses of temporal width ⁇ T and of periodicity Tb.
- the transmission system used may have the structure of an interferometer as Figure 12 shows it.
- the retarder 13 then comprises the separator element of the interferometer. The particle flow is thus separated into two parts sent to the two arms of the interferometer.
- the attenuator can, for example, use the auxiliary stream as a synchronization signal "sync" from the transmitter to the receiver.
- the decoder 3 then makes or not pass the pulse of the other arm of the interferometer in a delay line of identical duration ⁇ T / 2.
- the self-timer 13 and the decoder 3 have chosen the same delay 0 or ⁇ T / 2, then the probability of detecting a photon is 100% in one of the output channels (channel a) and zero in the other channel ( track b). If the self-timer 13 and the decoder 3 have chosen different delays, then the probability of detecting a photon is 50% in each channel.
- the particle counter 31' can, for example, be replaced by the device presented by the Figure 11 (b) if the pulses transmitted are in a minimal state.
- An additional advantage of temporal ambiguity cryptography compared to polarization ambiguity is that the probability that an additional advantage of temporal ambiguity cryptography compared to polarization ambiguity is that the probability that decoder 3 detects a photon is greater when the decoder 3 uses the two observation windows.
Abstract
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP01993992A EP1342338A2 (fr) | 2000-11-10 | 2001-11-09 | Procede et systeme de transmission par cryptographie quantique |
US10/416,187 US7298848B2 (en) | 2000-11-10 | 2001-11-09 | Quantum cryptography transmission method and system |
AU2002223046A AU2002223046A1 (en) | 2000-11-10 | 2001-11-09 | Quantum cryptography transmission method and system |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR0014488A FR2816779B1 (fr) | 2000-11-10 | 2000-11-10 | Procede et systeme de transmission par cryptographie quantique |
FR00/14488 | 2000-11-10 |
Publications (2)
Publication Number | Publication Date |
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WO2002039639A2 true WO2002039639A2 (fr) | 2002-05-16 |
WO2002039639A3 WO2002039639A3 (fr) | 2002-07-25 |
Family
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Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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PCT/FR2001/003500 WO2002039639A2 (fr) | 2000-11-10 | 2001-11-09 | Procede et systeme de transmission par cryptographie quantique |
Country Status (5)
Country | Link |
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US (1) | US7298848B2 (fr) |
EP (1) | EP1342338A2 (fr) |
AU (1) | AU2002223046A1 (fr) |
FR (1) | FR2816779B1 (fr) |
WO (1) | WO2002039639A2 (fr) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1687921A1 (fr) * | 2003-11-12 | 2006-08-09 | Magiq Technologies, INC. | Auto-etalonnage de detecteur dans des systemes qkd |
WO2008077833A1 (fr) * | 2006-12-22 | 2008-07-03 | Politecnico Di Milano | Générateur de nombres aléatoires et procédé de génération de ceux-ci |
Families Citing this family (8)
Publication number | Priority date | Publication date | Assignee | Title |
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US7620182B2 (en) * | 2003-11-13 | 2009-11-17 | Magiq Technologies, Inc. | QKD with classical bit encryption |
JP4709826B2 (ja) * | 2004-03-19 | 2011-06-29 | マジック テクノロジーズ,インコーポレーテッド | Qkdシステムのレーザオート・キャリブレーション |
FR2879381B1 (fr) | 2004-12-15 | 2008-12-26 | Thales Sa | Systeme de distribution quantique de cle de cryptage a variables continues |
FR2884662B1 (fr) * | 2005-04-15 | 2007-06-01 | Thales Sa | Systeme de distribution quantique de cle par codage temporel |
GB2430123B (en) * | 2005-09-09 | 2008-01-23 | Toshiba Res Europ Ltd | A quantum communication system |
US10756891B2 (en) * | 2014-04-09 | 2020-08-25 | The Boeing Company | Secure data communication |
US10887093B2 (en) * | 2015-08-14 | 2021-01-05 | Nokia Technologies Oy | On-chip continuous variable quantum key distribution system with polarization and frequency division multiplexing |
CN112205996B (zh) * | 2020-11-01 | 2023-05-26 | 南昌华亮光电有限责任公司 | 基于光子随机偏移量的图像加密系统与方法 |
Citations (1)
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EP0887967A1 (fr) * | 1997-06-23 | 1998-12-30 | Vrije Universiteit Brussel | Procédé de transmission d'une nouvelle clé crypthographique et dispositif y relatif |
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FR2565445B1 (fr) * | 1984-06-04 | 1986-10-10 | France Etat | Demodulateur de frequence et recepteur d'emission de television a multiplexage temporel en comportant application |
US5140636A (en) * | 1985-05-02 | 1992-08-18 | The United States Of America As Represented By The Secretary Of The Navy | Interferometric optical fiber data link |
US4962530A (en) * | 1987-09-10 | 1990-10-09 | Computer Security Corporation | System for cryptographing and identification |
US5243649A (en) * | 1992-09-29 | 1993-09-07 | The Johns Hopkins University | Apparatus and method for quantum mechanical encryption for the transmission of secure communications |
US5675648A (en) * | 1992-12-24 | 1997-10-07 | British Telecommunications Public Limited Company | System and method for key distribution using quantum cryptography |
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US5757912A (en) * | 1993-09-09 | 1998-05-26 | British Telecommunications Public Limited Company | System and method for quantum cryptography |
KR960705433A (ko) * | 1993-09-09 | 1996-10-09 | 사이먼 크리스토퍼 로버츠 | 양자 암호 작성법을 사용하는 키 통신 방법 및 시스템(system and method for key distribution using quantum crypto graphy) |
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- 2001-11-09 AU AU2002223046A patent/AU2002223046A1/en not_active Abandoned
- 2001-11-09 EP EP01993992A patent/EP1342338A2/fr not_active Withdrawn
- 2001-11-09 WO PCT/FR2001/003500 patent/WO2002039639A2/fr not_active Application Discontinuation
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Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1687921A1 (fr) * | 2003-11-12 | 2006-08-09 | Magiq Technologies, INC. | Auto-etalonnage de detecteur dans des systemes qkd |
EP1687921A4 (fr) * | 2003-11-12 | 2008-03-12 | Magiq Technologies Inc | Auto-etalonnage de detecteur dans des systemes qkd |
WO2008077833A1 (fr) * | 2006-12-22 | 2008-07-03 | Politecnico Di Milano | Générateur de nombres aléatoires et procédé de génération de ceux-ci |
Also Published As
Publication number | Publication date |
---|---|
FR2816779A1 (fr) | 2002-05-17 |
US20040062396A1 (en) | 2004-04-01 |
FR2816779B1 (fr) | 2003-03-07 |
EP1342338A2 (fr) | 2003-09-10 |
AU2002223046A1 (en) | 2002-05-21 |
US7298848B2 (en) | 2007-11-20 |
WO2002039639A3 (fr) | 2002-07-25 |
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