INTRODUCTION
C ONTEXTE GÉNÉRAL ET OBJECTIF DU STAGE
Cybersecurity is undoubtedly one of the major technological challenges of the 21st century Traditionally, communication security relies on classical cryptography, which is closely tied to the complexity of mathematical problems However, in recent years, Quantum Cryptography (QC) has emerged as a viable alternative for securing communications The fundamental concept of QC is to utilize Heisenberg's uncertainty principle to prevent eavesdroppers from gaining any useful information from a data transmission In essence, the uncertainty principle is central to quantum computing and serves as the cornerstone for the unconditional security of associated communications.
In 2003, the European project SECOQC was launched to develop a secure network utilizing quantum technologies This initiative involves multiple partners, including quantum physics laboratories, with ENST-Paris responsible for the network architecture and security validation A specific study project titled "Enhancing the Security of Aeronautical Communications Using Quantum Cryptography" is a collaboration between EUROCONTROL and ENST-Paris under the SECOQC framework, which began on February 17, 2004, and was presented on December 9, 2004, at the EUROCONTROL Experimental Centre (EEC) The primary aim of this project is to improve communication security in the aviation sector through advanced quantum cryptographic methods.
1 – étudier profondément le protocole d’échange de clef quantique BB84 (voir le rapport de Mlle Nguyen Thanh-Mai)
2 – examiner la faisabilité de l’intégration de la CQ dans les réseaux de satellites
3 – renforcer la sécurité des communications du réseau ATN en utilisant la CQ
This report provides a bibliographic study of CQ systems in open air and an overview of satellite networks, essential for addressing problem (2) as outlined by M Nguyen Toan-Linh-Tam Additionally, it tackles problem (3) by exploring a concrete quantum solution suitable for secure communications based on PKI within the ATN network The possibility of constructing a secret key distribution infrastructure using quantum mechanics is also examined For a complete version, please refer to: http://www.eurocontrol.int/care/innovative/care2/ENST/WP3.pdf.
I NTRODUCTION DE LA CRYPTOGRAPHIE QUANTIQUE
Classical secure communications rely on a secret key known only to the sender, Alice, and the recipient, Bob This system, known as symmetric key encryption, can be secure when using the one-time pad method, such as the Vernam cipher However, a challenge arises in securely transmitting the key between Alice and Bob without interception by an eavesdropper, Eve To address this issue, public key systems are typically employed, which leverage the mathematical difficulty of factorizing large numbers.
(1) Pour plus détaillé, veuillez-vous consulter le rapport de Mlle Nguyen Thanh-Mai
For more detailed information, please refer to Mr Nguyen Toan-Linh-Tam's report on large integers Currently, efficient algorithms to solve these problems remain elusive Consequently, a classical cryptographic system is deemed secure if an adversary requires an unreasonable amount of computational power to decrypt a message within a reasonable timeframe.
While it may seem pessimistic, it's conceivable that someone has already discovered, or will discover, efficient algorithms to solve the factorization problem in a reasonable time frame with manageable computational power Furthermore, the advent of quantum computers could easily compromise current cryptographic systems due to their immense processing capabilities Fortunately, these risks can be mitigated through the use of quantum cryptography, which is secured by the principles of quantum physics In fact, we leverage these laws to ensure robust security features.
1 – Mesure en mécanique quantique : Toute mesure perturbe le système observé, autrement dit, pour une mesure, il faut qu’il y a des interactions entre le système observé et l’appareil de mesure
2 – Théorème de non-clonage : il est impossible de dupliquer un état quantique arbitraire
Alice and Bob aim to exchange a secret message while Eve acts as an eavesdropper Alice encodes each bit of the message into a photon and transmits a series of photons to Bob If Eve intercepts and measures the photons, Alice and Bob can detect this interception due to the unique properties of quantum communication, prompting them to establish a new transmission until successful However, the speed of secure quantum transmissions is currently limited by physical devices, with a record speed of about 1000 bits per second, which is only suitable for secret key distribution Therefore, the term "quantum cryptography" typically refers to "quantum key distribution," a convention followed in this report, focusing solely on this type of quantum cryptography.
P LAN DU RAPPORT
Ce rapport est divisé en 4 parties :
This report will begin by addressing several key issues: a brief history of free-air CQ systems in Chapter 2.1, an overview of communication satellite networks in Chapter 2.2, and the current architecture and methods for securing ATN network communications in Chapter 2.3.
The second part will begin with an overview of the integration of quantum technology into satellite networks, aimed at achieving unconditional global security through satellites Following that, I will present solutions and experimental scenarios for each type of communication within the ATN network in Chapter 3.2.
Je présenterai quelques analyses des résultats obtenus au chapitre 4 et terminerai ce rapport par quelques conclusions au chapitre 5.
CRYPTOGRAPHIE QUANTIQUE EN AIR LIBRE - RÉSEAU DE
C RYPTOGRAPHIE Q UANTIQUE EN AIR LIBRE
Advancements in physical technology are crucial for the development of Quantum Cryptography (QC) A typical QC system consists of at least one emitter (photon source), one receiver (detector), and a quantum channel Fiber optic links and free-space connections are the two primary solutions for the quantum channel, with most researchers currently utilizing fiber optics to transmit photons from Alice to Bob However, fiber optic systems are limited to a distance of 150 km due to fiber loss and detector noise Additionally, fiber optic connections may be impractical due to geographical challenges Consequently, there is a growing effort to develop systems based on free-space links, where photons are transmitted between two telescopes over longer distances.
The first demonstration of the free-space CQ system took place at the IBM Thomas J Watson Research Center, achieving a distance of 32 cm With advancements in technology, the latest results have reached an impressive distance of 23.4 km Theoretical calculations suggest the potential for free-space communication up to 1600 km, making it suitable for secure key exchange via satellite This chapter will explore the state of the art in free-space CQ systems and assess the feasibility of integrating satellite communications for enhanced connectivity.
CQ pour une distribution de clef globale, qui est le but final de tels systèmes
Quantum links in free space have been successfully implemented in CQ systems using low-power laser pulses for several years Free-space transmission is one of two solutions for quantum channels, offering several advantages over fiber optic transmission Notably, the atmosphere provides an advanced transmission window around the 800nm wavelength, where photons can be easily detected by high-efficiency commercial detectors Additionally, the atmosphere is only weakly dispersive and essentially isotropic at these wavelengths, ensuring that the polarized state of a photon remains unchanged.
However, there are also disadvantages associated with free-space quantum links Firstly, unlike signals transmitted through optical fibers where energy is protected and confined to a small space, energy transmitted in free space disperses, resulting in significant transmission losses Secondly, background light, such as daylight or moonlight at night, can interfere with the receiver, leading to errors in dark count Lastly, it is evident that the performance of free-space quantum systems is heavily dependent on atmospheric conditions.
In the 1970s, Stephen Wiesner, H Bennett from IBM, and G Brassard from the University of Montreal introduced the concept of quantum cryptography (CQ) Although the idea is straightforward enough that a first-year quantum mechanics student could have conceived it, the theory of CQ has now matured With the growing importance of information security, physicists are increasingly viewing quantum mechanics not just as a fascinating theory filled with paradoxes, but as a promising tool for new technologies.
The first protocol used in quantum cryptography (QC) was proposed in 1984 by H Bennett and G Brassard, known as BB84 Following this, more efficient protocols were introduced, including the two-state protocol, the six-state protocol, and the Einstein-Podolsky-Rosen protocol However, most quantum cryptography experiments to date have been constrained to the BB84 protocol due to its simplicity and the limitations of physical devices.
One of the most critical aspects of a quantum communication (QC) system is the selection of the photon source and photon detector QC fundamentally relies on single-photon Fock states, which are challenging to achieve in practice Currently, practical experiments utilize weak laser pulses or entangled photon pairs, where the distribution of photons or entangled pairs follows Poisson statistics Significant losses in the quantum channel can lead to severe security risks in the exchanged key, highlighting the importance of the "photon gun." Regarding photon detectors, various techniques can be employed, including photomultipliers, avalanche photodiodes, multi-channel detectors, and superconducting Josephson junction detectors.
Aujourd'hui, le meilleur choix de la longueur d'onde pour les systèmes CQ en air libre est de
Efficient detectors like avalanche photodiodes (APDs) are commercially available at 800 nm The receiver utilizes a combination of spectral filtering, spatial filtering, and timing discrimination, typically within a few nanoseconds, to reduce counting errors However, free-space transmission is restricted to line-of-sight links, making it challenging to aim laser beams at moving targets.
Despite advancements in quantum communication theory, free-space quantum communication systems remain unpopular The first experiment was conducted by Bennett and colleagues at IBM in the early 1990s over a distance of 30 cm Since then, there have been several other significant free-space experiments.
Année Auteur Lieu Distance Contexte
1998 R.Hughes Los Alamos ~1km au soir
2000 R.Hughes Los Alamos 1.6km au jour
2001 J.Rarity QinetiQ 1.9km au soir
2002 R.Hughes Los Alamos Plus de 10km
Tableau 2-1 Expériences du système en air-libre
The results obtained by P Morris represent a significant advancement in quantum key exchange systems By utilizing larger and lighter telescopes, optimized filters, and anti-reflection technology, combined with more sophisticated automatic pointing and routing hardware, these systems could achieve stability with a loss of up to 34dB— the maximum acceptable loss for a quantum communication system— and potentially reach distances exceeding 1600 km This opens up the exciting possibility of exchanging quantum keys with low Earth orbit satellites, functioning as secure relay stations, enabling the unbreakable secure exchange of secret keys between any two arbitrary locations worldwide.
Pour une meilleure compréhension, nous étudierons le succès le plus récent du système CQ en air libre de P Morris
2.1.2 Expérience réussie la plus récente
From September 2001 to January 2002, P Morris tested his semi-portable CQ system in open air between two mountain peaks, Karwendelspitze (2244m) and Zugspitze (2960m), in southern Germany, for secure key exchange The distance between the peaks was 23.4 km The high-altitude laser beam path significantly reduced atmospheric disturbance effects seen in previous lower-altitude experiments However, it introduced new requirements for stability against temperature fluctuations, reliability in extreme weather conditions, and ease of alignment.
Alice, the sender, encodes random binary numbers into weak light pulses using linear polarization to represent a value of 1 and orthogonally polarized pulses for a value of 0 To prevent eavesdropping, the number of photons per pulse is limited to less than one, typically set at 0.1 photons The coding basis is randomly changed by rotating the polarization by 45° for half of the pulses sent Bob, the receiver, detects the received pulses by converting light into macroscopic electronic impulses, separating the two polarizations through a polarizing beam splitter to register a value of 0 or 1 based on the detected polarization A random switch selects the coding basis of either 0° or 45° for measuring the received pulse, giving each photon a 50% chance of matching the coding basis Due to initial and transmission attenuation, only a few pulses are detected by the receiver Detected pulses are stored, and at the end of transmission, Bob uses a classical channel to inform Alice which pulses were received and their measurement basis Lost pulses and those measured in a different basis are discarded, ensuring both parties maintain an identical random key Any remaining discrepancies signal potential eavesdropping; if an eavesdropper measures a pulse's polarization, the photon is destroyed and does not reach Bob Although the eavesdropper can choose coding bases and resend copies, this strategy fails because they will incorrectly measure the basis half the time, resulting in a 25% error rate compared to the normal 50%.
A certain level of error rate may naturally arise from imperfections in the devices used; however, to ensure absolute security, any error must be attributed to interception Consequently, errors below a certain threshold will be corrected, and potential knowledge regarding a spy's key will be eliminated through privacy amplification protocols.
Il est pareil au comparaison à tous les autres systèmes CQs en air libre, le système CQ de P.Morris se compose de 3 composants principaux:
- Canal quantique (en air libre)
The transmitter, designed around an 80 mm diameter telescope, utilizes a digital I/O card that generates 2-bit random signals at 10 MHz, synchronized to a reference clock These signals are employed in the pulse driver to randomly activate one of four lasers, each emitting pulses of 500 ps duration and a wavelength of 850 nm, within a miniature source module This compact source utilizes polarization to encode weak pulses instead of single photons The four lasers are combined using a spatial filter with a mirror lens and conical relay, with each laser adjusted to produce one of four polarizations: 0°, 90°, 45°, or 135° These lasers illuminate a spatial filter consisting of two pinholes, each with a diameter of 100 µm, positioned 9 mm apart.
Due to the limited overlap between the emission modes of the four laser diodes and the filter mode, the initial bright laser pulses are attenuated to approximately "one photon per pulse." This system utilizes pulses containing 0.05 to 0.5 photons per pulse, with the actual attenuation finely adjustable by manipulating the current on the diode and accurately calibrated using a spatial filter This filter eliminates all spatial information regarding which diode emitted the laser Additionally, spectral information is secure from eavesdropping, as the spectra of the four laser diodes can overlap within a width of 3 nm in pulsed mode A continuous wave beam can be injected using an auxiliary mirror for alignment within the same spatial filter as the weak pulses, while photon counting can be calibrated by inserting a FM mirror and using a photon counter.
R ÉSEAUX DE SATELLITES DE COMMUNICATION
In the past, satellites were considered exotic and secretive devices primarily used by military organizations for navigation and intelligence purposes Today, they play a crucial role in our daily lives, enabling communication through radio, television, and telephone transmissions worldwide Before the advent of satellites, long-distance transmissions were challenging, if not impossible, as signals could only travel in straight lines and could not bend around the Earth's curvature With satellites in orbit, signals can be sent instantly into space and redirected to other satellites or directly to their intended destinations.
A communication satellite acts as a wireless relay station, establishing a link between two geographically distant locations Due to its high altitude, satellite transmissions can cover a vast area on Earth Typically, each satellite is equipped with a variety of transponders, which consist of a transmitter, a receiver, and an antenna tuned to a specific assigned spectrum.
The incoming signal is amplified and then re-emitted at a different frequency Most satellites simply transmit what they receive, traditionally used for applications like TV broadcasting and voice telephony In recent years, the use of satellites for data packet transmission has evolved, typically being utilized in WAN networks, where they provide primary connections to other geographically dispersed WANs and LANs.
Satellites typically operate across multiple frequency bands, utilizing separate carrier frequencies for uplink and downlink communications The most common frequency bands are illustrated in Table 2.3 While the C band was prevalent in the first generation of satellite communication systems, it faces congestion due to terrestrial microwave links using similar frequencies Current trends favor higher frequencies, such as Ku and Ka bands, although rain attenuation poses significant challenges for both Additionally, the higher frequency devices, especially in the Ka band, tend to be quite expensive.
C 4 (3.7 – 4.2) 6 (5.925 – 6.425) Interférence avec le liens vers bas
Ku 11 (11.7 – 12.2) 14 (14 – 14.5) Atténuation due à la pluie
L/S 1.6 (1.610 – 1.625) 2.4 (2.483 – 2.500) Interférence avec la bande ISM
Tableau 2-3 Fréquences des bandes communs
The area of the Earth's surface covered by a satellite transmission beam is referred to as the "footprint" of the satellite transponder The uplink is a highly directional, point-to-point connection that utilizes a large parabolic antenna at the ground station In contrast, the downlink can have a broad footprint to effectively cover a substantial area.
The "small spot beam" can be utilized to focus high energy at a more cost-effective and compact ground station Additionally, some satellites have the capability to dynamically reorient their beams, allowing them to adjust their coverage area.
Satellites can be positioned in various orbital sizes and shapes, including circular or elliptical orbits Based on their orbital radius, all satellites can be classified into one of three categories.
- Orbite Basse De la Terre (LEO)
- Orbite Moyenne De la Terre (MEO)
Quelques caractéristiques de 3 types satellites sont montrés dans le tableau 2.5
Altitude 500km- 1500km 5000km-12000km 35786km
Avantages Cỏt de lancement réduit, temps d’autour très court, perte réduite
Cỏt de lancement moyen, temps d’autour court
Couvrir 42.2% de la surface de la terre, vue constante
Désavantages Durée de vie très court 1-3 mois, rencontre la ceinture de rayonnement
Plus de retarde Plus de perte
Temps d’autour trop large, très cỏteux
Tableau 2-4 Caractéristiques des satellites différents
Satellites can be categorized based on their payload weight Satellites weighing between 800 to 1000 kg are classified as "small," while those exceeding this weight are referred to as "large" satellites Typically, geostationary satellites (GEO) fall into the "large" category, whereas low Earth orbit satellites (LEO) can belong to either classification.
Quelques protocoles des communications pour les satellites:
ALOHA is a fundamental protocol used in radio packet communications Its straightforward structure makes it easy to manage; however, it poses challenges in accurately receiving packets when collisions occur.
Frequency Division Multiple Access (FDMA) is the oldest and still one of the most common channel allocation methods In this technique, the available bandwidth of a satellite channel is divided into multiple frequency bands, allowing different stations to operate simultaneously.
Time Division Multiple Access (TDMA) is a method where channels are multiplexed in a sequential manner In this approach, each ground station is allocated the right to transmit only during specific, predetermined time slots.
Code Division Multiple Access (CDMA) utilizes a hybrid of time/frequency multiplexing and is a form of spread spectrum modulation Although it is a relatively new method, there are hopes that it will become more common in the future of satellite communications.
Accès Multiple de la Réservation de Paquet (PRMA) : C'est une forme améliorée de TDMA qui combine TDMA avec les techniques d'ALOHA Encoché
Currently, there are several modern satellite networks, including IRRIDIUM, INMARSAT M, GLOBALSTAR, ODYSSEY, ICO, and GPS To gain a better understanding of satellite networks, we will focus on GPS, one of the most well-known satellite systems.
The Global Positioning System (GPS) consists of a constellation of 24 satellites orbiting the Earth, enabling users with GPS receivers to pinpoint their exact geographic location Typically, the accuracy ranges from 10 to 100 meters for most devices, but specialized equipment used by military organizations can achieve precision within one meter Today, GPS technology is widely utilized in various scientific fields and has become affordable enough for nearly anyone to own a GPS receiver.
Figure 2-3 Système de Positionnement Globale
The GPS, originally owned and operated by the United States Department of Defense, is now accessible for public use worldwide Its key features include precise location tracking, navigation assistance, and real-time data availability, making it an essential tool for various applications.
C OMMUNICATIONS SÉCURISÉES DU RÉSEAU ATN
Le figure 3.1 montre les communications entre les entités du Réseau de Télécommunications aéronautique (ATN)
Figure 2-4 Communications dans le réseau ATN
On peut diviser les applications dans l’ATN en 2 catégories [10]:
The Context Management Application (CMA) is a key component of the A/S applications It facilitates the integration of the AES within the ATN network, enabling seamless communication and interaction with other A/S applications and services.
In general, the security of the ATN network employs solutions similar to those used for secure Internet applications However, the use of wireless connections in A/S applications introduces a new set of threats to an aircraft's operational safety The ICAO has identified primary threats to A/S applications, including Denial of Service (DoS), masquerading, and information modification The key security requirements can be summarized as follows:
- Authentification des sources de message
- Authentification de la source d'informations de cheminement
(1) CPLDC : Controller-Pilot Data Link Communications
The security requirements established by ICAO focus primarily on data integrity and entity authentication However, ICAO's security framework also facilitates the protection of user information, as the ATN security architecture is built upon a Public Key Infrastructure (PKI).
In the context of ATN network security, when an aircraft system known as AES seeks to communicate with a ground station application called GS, such as the CPDLC application, AES and GS typically collaborate to execute a fundamental scenario.
- Étape 0 : Initialisation des services de PKI pour les entités du réseau ATN qui vont participer aux communications sécurisées telles que l’AES, l’application de gestion du contexte (CMA), l’application CPDLC
- Etape 1 : AES crée une demande de loger dans l’application CPDLC et puis l'envoie à CMA
- Etape 2 : CMA envoie une réponse d’acceptation à AES
- Etape 3 : AES et CPDLC calculent une clef secrète de session commune grâce aux donnộes reỗues de premiốre ộtape et deuxiốme ộtape
- Etape 4 : AES et CPDLC sécurisent les messages échangés en employant cette clef de session
Le tableau 3.2 sur la page suivante montre ce scénario en plus détail
In the above scenario, AES holds two secret session keys: one for secure communication with CMA and the other for CPDLC Currently, this scenario is enabled by the support of the ATN PKI, which can provide the following cryptographic modules.
- Module du Chiffrement : Chiffrement asymétrique ou symétrique
- Module de Signature Numérique : Chiffrement Symétrique et Fonction de Hachage
- Module de Accord de Clef : Chiffrement Asymétrique
- Module de Authentification de Message : Fonction de Hachage
The inclusion of PKI in A/S messages will significantly increase the load on communication channels with limited bandwidth, as a standard X.509 certificate is approximately 20KB in size Therefore, it is essential to consider solutions like compression to minimize the size of secure messages.
Typically, Certificate Revocation Lists (CRLs) are quite large, making it impractical to transmit them over A/S links with limited bandwidth To address this issue, application private keys should only exist for a short duration, such as the length of a flight Therefore, one viable solution is to manually download the keys to AES before the flight, as AES is usually located in a physically secure airport environment managed by ATN.
Avion (AES) Application de Gestion du
- Clef privée pour la Signature numérique (DS) de AES
- Clef privée pour l’Accord de Clef (KA) de AES
- Clef KA privée de CMA
- Clef KA privée de CPDLC
- créer une demande de loger au CPDLCA basée sur ID de AES, ID de CPDLCA, temps
- signer sur cette demande en utilisant sa clef DS
- appeler les services PKI pour retenir le certificats de AES et CPDLCA
- Authentifier la demande de loger vient de AES en utilisant la clef
- calculer une clef de session avec CMA en utilisant la clef KA publique de AES, la clef KA privée de CMA
- calculer la clef de Session avec CMA basée sur la clef KA pub de CMA, la clef KA privée de AES
- authentifier la réponse vient de CMA en utilisant la code d’authentification
- créer la réponse d’accepte en utilisant la clef KA pub de CMA, la clef KA pub de CPDLC, la clef de Session avec CMA, la code d’authentification
Calculer la clef de Session
- calculer la clef de Session avec CPDLCA en utilisant la clef KA privée de AES, la clef KA public de CPDLCA
- calculer une clef de Session avec CPDLCA en utilisant la clef KA publique de AES, la clef KA privée de CPDLCA
- sécuriser les messages échangées en utilisant la clef de Session avec CPDLC
- sécuriser les messages échangées en utilisant la clef de Session avec CPDLC
Tableau 2-5 Communications Air/Sol basées sur le PKI
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CRYPTOGRAPHIE QUANTIQUE ET RÉSEAU DE TÉLÉCOMMUNICATION AÉRONAUTIQUE (ATN)
I NTÉGRATION DE LA CRYPTOGRAPHIE QUANTIQUE ET LES SATELLITES
Currently, the most suitable quantum system for long-distance communication is photonic technology While other atoms, such as molecules and ions, are being researched, their practical application for quantum communication remains unfeasible in the near future Therefore, photons are the sole viable option for long-distance quantum communication.
The use of satellites for photon distribution offers a unique solution for long-distance quantum communication networks, effectively addressing the primary limitation of current technology, which is approximately 100 km for fiber optic or free-space links Although it may seem different, free-space quantum communication over a 2 km distance on the ground is comparable to that between a terrestrial station and a satellite at an altitude of 300 km Current photon sources and detectors used in traditional laser communication systems cannot be directly applied to quantum systems; however, the experience gained from these technologies can serve as a foundation for developing the necessary qualified components for free-space quantum applications.
In free-space quantum communication (CQ) based on satellites, the primary challenge lies in the orientation of the laser beam, as atmospheric disturbances can significantly affect transmission Another crucial issue is minimizing the size and weight of the equipment, which must be installed on the satellite Key parameters for effective transmission include the laser wavelength, transfer rate, modulation format, and reception technique An essential subsystem known as the Pointing, Acquisition, and Tracking (PAT) system is responsible for beam orientation, link acquisition, and automatic terminal tracking Due to the narrow beam widths involved in communication, the PAT requires highly sophisticated designs and electro-mechanical and electro-optical components that meet exceptional technological standards The main factors influencing link capacity include telescope size, transmitted laser power, distance, and receiver sensitivity, alongside considerations of terminal mass, volume, and energy consumption Existing examples of free-space quantum links include the SILEX inter-satellite links by the European Space Agency (ESA) and recent satellite-to-ground links established between the GEO ARTEMIS satellite and the OGS optical ground station in Tenerife.
While air-based links offer intriguing advantages, such as immunity to atmospheric disturbances and the correlation between satellite positions, they currently face significant technological and financial challenges compared to alternative solutions that have at least one terminal on the ground Most quantum experiments require high-level flexibility at the receiver due to polarization control and data analysis Therefore, it is more practical to position the transmitter on the satellite while keeping the receiver in easily accessible ground laboratories.
Due to their relative stationary position, terminals on GEO satellites do not require as sophisticated a PAT system as those on LEO satellites Typically, these GEO terminals are utilized for long-duration experiments However, the link attenuation and costs are significantly higher for GEO links compared to LEO Therefore, we recommend using a LEO platform with a more complex PAT system for initial experiments.
Dans le rapport de M.Nguyen Toan-Linh-Tam, nous avons analysé plus en détail les choses nécessaires, les scénarios possibles, et les perspectives du CQ aidant par satellite.
R ENFORCEMENT DE LA SÉCURITÉ DANS LE RÉSEAU ATN
It is crucial that any solutions or enhancements for ATN security are implemented within the current framework of ATN These improvements must be fully compatible with ATN and developed progressively over time.
A CQ system for the ATN network can be viewed as a Quantum Key Infrastructure (QKI) that offers shared confidential keys to encrypt the communication channel between two entities.
The main drawbacks of CQ technology stem from distance limitations, with a maximum range of 130 km for optical fiber and 23 km for free-space links To build an effective QCKI, it is essential to consider two key concepts: quantum relays and CQ data relays It is important to differentiate between CQ data relays and quantum relays.
A quantum relay would redirect and manipulate the quantum state of a photon without directly measuring it In contrast, a classical data relay consists of devices that can establish secure communication using advanced technology.
CQ avec l'ộlộment prộcộdent de la chaợne et une autre communication sộcurisộe diffộrente avec l'ộlộment suivant de la chaợne :
- Le relais k établit un lien de communication radio chiffré avec le relais k-1 basé sur une clef partagée grâce à la CQ
- Le relais k reỗoit des donnộes chiffrộes du relais k-1 et ces donnộes reỗues sont déchiffrées et stockées dans la mémoire du relais k
The relay k establishes a secure radio communication link with relay k+1 using a different key, CQ The data stored in memory is encrypted with this key CQ before being transmitted to relay k+1.
As previously mentioned, the ATN network consists of two main categories of applications: Air/Ground (A/G) and Ground/Ground (G/G) For the purpose of this discussion, we will assume that all the necessary physical equipment for CQ technology is functioning perfectly.
Et laissez-nous voient le scénario pour l'intégration de QCKI dans chaque type d'applications d'ATN
3.2.1 Solution pour les applications Air/Sol
One of the main drawbacks of Public Key Infrastructure (PKI) in the Aeronautical Telecommunications Network (ATN) is the limited bandwidth of Air/Ground links For instance, at a European airport, PKI can be utilized to distribute secret keys to the Aeronautical Encrypted System (AES) on the ground prior to takeoff However, there appears to be no viable solution using PKI for AES once it is airborne in European airspace In this context, Quantum Key Infrastructure (QCKI) may emerge as a superior alternative due to its inherent flexibility.
The Quantum Key Distribution Infrastructure (QKDI) is essential for delivering shared confidential keys for encryption between two endpoints In ATN applications, one endpoint is always an aircraft (AES), while the other is a ground station (GS) connected to the ATN network.
Typically, the chosen quantum channel should be a free-space quantum channel, as airplanes operate in the sky However, if the aircraft is on the ground, fiber optic channels can be utilized instead, provided the airplane is connected to the airport infrastructure Conversely, when the airplane is on the tarmac without a physical link to the airport infrastructure, the technology must adapt accordingly.
CQ en air libre doit être employée
With the support of QCKI, an aircraft can easily establish secure communication with A/S applications provided by the ATN network, as illustrated in the basic scenario depicted in Table 3-1 on the following page.
CQ technology has specific characteristics that are essential for developing an effective QCKI To ensure successful integration with A/S applications, it is crucial to understand the scenarios in which QCKI can operate Depending on the arrangement of the receiver and transmitter, as well as the type of photon sources used (single photon sources or entangled photon pairs), various scenarios can be envisioned for employing QCKI within the ATN network.
- source de photon simple au sol, voir la page 25
- source de photon simple sur l’avion, voir la page 25
- source de photon simple sur le satellite, voir la page 26
- source de photons intriqués au sol, voir la page 27
- source de photons intriqués sur l’avion, voir la page 27
- source de photons intriqués sur le satellite, voir la page 28
QCKI Avion (AES) Application de Gestion du Contexte (CMA)
- distribuer une clef secrète quantique pour la session entre AES et CMA
- recevoir la clef quantique secrète vient de QCKI
- recevoir la clef quantique secrète vient de QCKI
- chiffrer la demande de loger
- Authentifier la demande de loger vient de AES en utilisant cette clef quantique secrète
- - Authentifier la demande de loger vient de AES en utilisant cette clef quantique secrète
- Chiffrer la réponse d’accepte en utilisant la clef quantique secrète
- distribuer une autre clef quantique pour la session entre AES et CPDLCA
- recevoir la clef quantique secrète pour la session avec CPDLCA
- recevoir la clef quantique secrète pour la session avec AES
- sécuriser les messages échangées en utilisant la clef quantique pour la Session entre AES et CPDLCA
- sécuriser les messages échangées en utilisant la clef quantique pour la Session entre AES et CPDLCA
Tableau 3-1 Communications sécurisées Air/Sol par QCKI
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A ground-based single photon source is utilized, with the single photon emitter positioned at the ground station (GS) A laser link is established to a receiver located on the aerial transmission system (AES), employing the BB84 protocol to facilitate secure shared key negotiations, as illustrated in Figure 3-1 (a).
Figure 3-1 Source de photon single au Sol
A satellite can function as a quantum relay station, as illustrated in Figure 3.1 (b) Additionally, fiber technology can be utilized if the aircraft is grounded at a European airport, allowing for key distribution prior to takeoff.
Each aircraft is equipped with a single photon emitter, utilizing a low-power laser that employs the BB84 protocol This setup enables secure key exchange with a ground-based receiver, as illustrated in Figure 3.2 (a).
Figure 3-2 Source de photon single sur l’avion
A quantum relay satellite, like the one illustrated in Figure 3.2 (b), can be utilized for secure communications Additionally, if the aircraft is at a European airport, fiber optic technology can be employed to distribute keys prior to takeoff.
ANALYSE
We have explored a brief history of free-space quantum communication (CQ) systems, which represent one of two solutions for quantum channels The most significant challenges arise from the current imperfections in quantum physical devices Contrary to initial assumptions, the fundamental mechanisms of CQ are not overly complex Researchers are actively seeking improved devices, such as advanced photon guns and high-performance photon detectors Notably, quantum techniques are rapidly advancing, both theoretically and practically Many scientists believe that the era of quantum communication and quantum computing is imminent, prompting the need to anticipate scenarios that could leverage the advantages of CQ.
We have explored the role of satellites in establishing a secure global network The advantages of utilizing satellites for this purpose are significant, as discussed in section 3.1 regarding the integration of quantum communication (CQ) into satellite systems, with further insights provided by Mr Nguyen Toan-Linh-Tam However, the high costs associated with these experiments mean that only governments can effectively implement CQ through their policies and investments Due to time constraints, a detailed financial analysis of our scenarios was not conducted Nevertheless, if we succeed in this integration, we can envision a truly secure global network, as the security provided by quantum mechanics is unconditional and inviolable.
The article discusses six scenarios for implementing Quantum Communication (QC) in the Air/Ground applications of the ATN network It highlights that scenarios using single photon sources are quite similar to those employing entangled photon sources, despite their intrinsic differences An entangled photon source can function as a single photon source, whereas a pair of single photon sources is fundamentally different from an entangled source Theoretically, all proposed scenarios are compatible with the current secure solutions of the ATN network, allowing for testing with minimal changes to the existing infrastructure.
We have proposed the development of a quantum key distribution infrastructure aimed at achieving unconditional global security This strategy involves gradually replacing the outdated PKI-based infrastructure of the ATN network with a new quantum framework Although we have not yet obtained experimental evidence, our findings can serve as a foundational starting point for the necessary experiments in free-space quantum applications.
CONCLUSION
This report presents my contributions to the project on enhancing communication security within the ATN network The findings are significant, offering a solution for implementing quantum communication (QC) in the ATN network and proposing a highly flexible infrastructure for quantum key distribution (QKD) Specifically, I have developed a protocol and scenarios for QC implementation based on an analysis of the actual capabilities of quantum devices and the current state of the ATN network Additionally, I proposed a strategy for the gradual evolution of the QKD infrastructure, allowing it to coexist with the normal operations of the ATN network Notably, this strategy enables the periodic replacement of the public key infrastructure with the quantum key distribution framework.
Due to limited time and financial constraints, our results fell short of experimental claims, which is quite serious However, these experiments require significant investment that is beyond our reach Therefore, our theoretical results can be viewed as a starting point for the necessary experiments in free-space quantum cryptography applications I hope to further explore this fascinating topic in the future and participate in the experimental testing of our proposals.