Güvenli şekilde dost uçakları tanıma

Abstract

Son yıllarda havacılık sektörünün popülerliği hem sivil hem de askeri alanda artmıştır.Sivil havacılıkta kullanımları yoğun bir şekilde devam eden ve her geçen yılkullanımları giderek artan yolcu taşıma uçaklarına, kargo taşıma uçaklarına ek olarak;insansız hava araçları gibi araçların giderek yaygınlaşmaya başlaması ve drone gibiyeni nesil insansız hava araçlarının da popülerliğinin artması (gözlem ve insan-yüktaşıma faaliyetlerindeki kullanımlarının artması) bu sektörü her geçen yıl daha dagüçlü kılmaktadır ve sektörün zorlukları da giderek artmaktadır. Askeri havacılıktaise kullanımları yıllardır süregelen savaş uçakları, helikopterler gibi hava araçlarınaek olarak; yine gözlem için kullanılan insansız hava araçları ve savunma-saldırıiçin kullanılan silahlı insansız hava araçları, askeri havacılık alanını devletler içintakip edilmesi kaçınılmaz bir alan kılmaktadır. Sektörün mevcut alanlarındaki havaaraçlarının kullanımının artması ve yeni hava araçlarının kullanılmaya başlanması herne kadar herkesi memnun etse de, artan trafiğin yönetiminin her geçen gün zorlaşmasısektörün sorunlarından bir tanesi haline gelmiştir. Ayrıca artan bu kullanımla birliktegüvenlik konusu da gittikçe önem kazanmaktadır. Bu çalışmamızda savaş uçaklarındabulunan dost - düşman tanıma sistemlerine alternatif olabilecek aynı zamanda sivilhavacılıktaki güvenlik problemlerini de giderebilecek bir tanıma şeması geliştirdik.Bu tezde yetkisi olmayan uçakların kendilerini diğer uçaklara `dost` olarak tanıtmasınıengellemek amacıyla uçak filoları arasında kullanılabilecek bir tanıma (identification)şeması tasarlanmıştır. Bu şema havacılık iletişimdeki tanıma sorununa bir çözümolarak kullanılabilir. Yöntemimiz klasik şifreleme yöntemlerinin ve sıfır bilgi ispatıyöntemlerinin bir birleşimidir. Dost filolarda yer alan uçaklara, aynı filo içindeyer alan uçaklara aynı anahtarlar dağıtılmak üzere, birbirleriyle belirlenen benzerlikoranında benzeşen gömülü anahtarlar dağıtılmış ve kullandığımız matematiksel modelleiki filo arasında anahtarlarının benzerliğini anlama kıstası üzerinden bir tanımlamaşeması tasarlanmıştır. Zero Knowledge Proof tekniği sayesinde iki hava aracı arasındagömülü anahtarına dair hiçbir bilgi paylaşımı olmadan `dost` veya `bilinmeyen`olarak kategorileştirme işlemi yapılması amaçlanmıştır. Dost kategorisine giren havaaraçlarının mesajları bu iletişim sonrasında işlenirken, bilinmeyen olarak işaretlenenhava araçlarının mesajlarının dikkate alınmaması sağlanacaktır. Genel olarak buçalışmada sıfır bilgi ispatına dayanan yöntemle daha güvenilir bir tanıma sistemi sistemsunduk.

In last years, aviation industry has become more and more popular. In additionto being extensively used in air transportation and cargo transportation areas whichare continuing to be used intensively in civil aviation; the increasing popularity ofnew generation unmanned aerial vehicles such as drone (observation, human-cargotransport activities) makes this sector stronger and more challenging every year.Besides, the air vehicles such as combat aircraft, helicopters, which have been in usefor years in military aviation; the unmanned aerial vehicles that used for observationand armed unmanned aerial vehicles that used for defense-attack make the militaryaviation an inevitable subject to follow closey.Technological developments have undoubtedly improved their accuracy, consistency,effectiveness and system continuity of aviation navigation systems. System securityhas become a necessity in the sector to eliminate the threats of the aviationinfrastructure. Currently, there is no common vision, common strategy, objectives,standards, implementation models or international policies defining cyber security forcommercial aviation. It is a common responsibility of governments, airlines, airportsand manufacturers to ensure a safe aviation system and prevent cyber threats.Avionics which means aviation electronics covers all electronic systems used in anaircraft. These systems mainly perform navigation, communication, display and otherflight and duty functions. Military avionics systems are indispensable for manned,unmanned aircraft, missiles and weapons. These systems allow the aircraft to performdefense, attack and surveillance tasks. The main difference between the Avionicssoftware and the conventional embedded software is that the avionic software isoptimized for security and the legal arrangements that require the development processof the software. Avionics become an important discipline with the rapid developmentof new generation computers, communication hardware, software languages anddevelopment tools. With these developing areas, the avionics has expanded andbecome multi-disciplined.Although increased usage of vehicles in the existing areas and the newly comingaircrafts pleased everyone, overseeing and controlling of air traffic has become oneof the biggest problems in the sector. Even if we have developed PSR (PrimarySurveillance Radar) and SSR (Secondary Surveillance Radar) to control the air traffic,afterwhile these developed technologies become insufficient because of the increasedaircrafts. These radar systems were highly costly and inappropriate for the newlycoming air vehicles. In these radar systems, the vehicles has to communicate withthe ATC (Air Traffic Controller) tower to inform other air crafts and also has tocommunicate with ATC tower again to get the information from other air crafts.In order for the ATC towers to manage the airspace safely, each control unit must understand the status of each aircraft. Traditionally, the PSR and the SSR have fulfilledthis role in various ways since World War II. Both systems are designed at a timewhen radio transmission requires a great deal of financial investment and expertise.Therefore, these old systems were not given any security considerations because theywere assumed to be inaccessible. The rise of Software-Based Radio (SDR) overridesthis assumption and has enabled potential attackers to compromise the system withfewer resources. Without authentication of the basic protocols, data link level attacksare more difficult to detect for both aviation systems and users of these systems thanfor attacks on traditional analog technologies such as the audio communication systemor primary surveillance radar (PSR).A new communication technology named ADS-B (Automatic DependentSurveillance-Broadcast) has developed and started to be used in air craft vehicles.Using the global navigation system, ADS-B helps aircraft find their positionindependently. Aircrafts can periodically send their altitude, speed and other relevantdata with the help of a digital data connection that communicates with air-to-air andair-to-land systems. ADS-B is a completely new paradigm for air traffic control. Eachparticipant gets their position and speed using a built-in GPS ( Global PositioningSystem) receiver. The location is then periodically broadcasted by a transmittersubsystem called ADS-B Out with a message (typically twice per second). Themessages are received and processed by ATC towers on the ground or by nearbyaircraft if the air craft is equipped with ADS-B In. One of the security problem ofADS-B is that it is impossible to detect the identification of the ADS-B messagesender aircraft.The critical importance of IFF (Identification Friend or Foe) systems has led to manystudies for it. IFF system is installed in vehicles such as warplanes and warships. It is aradar transponder that responds correctly with an encrypted message that describes theaircraft or ship `friend` when interrogated by appropriate radar signal. Interrogativedevices are placed in search, surveillance and capture radars. It is also installed in theguidance systems of certain antiaircraft missiles. All aircraft and ships equipped withthe IFF may be targetted if they do not react correctly when detected by the radar. InAir Defense Systems, identification and access control of friendly-foe aircraft are thenecessary protection mechanisms.Furthermore, security in communication is becoming more and more important withthis increased usage. We have created an identification scheme that can be analternative to the identification of friend or foe systems in combat aircraft, which canalso solve the security problems in civil aviation.There are many different algorithms that provide secure communication incryptography. In this study, we will use two algorithms, namely Secret Sharing andZero Knowledge Proof (ZKP). ZKP systems were introduced in 1985 by Goldwasser,Micali and Rackoff. This protocol is based on a Prover convincing a Verifier to validateknowledge without revealing any information beyond the reality of information. ZKPtechniques are important techniques used in cryptographic algorithms.Interpolation is a basic mathematical technique to bring something complicated to asimple or at least less complex structure.Interpolation is an effective tool to make highprecision approximations. These methods generally provide numerical approaches tocalculate complex function values and to evaluate differential equations. Polynomialinterpolation methods date back to 17th century. Polynomial interpolation provides a simple and good way to predict the analytical expression, specifically a function, in aregion stretched by the measured points. The Newton Divided Difference method is anumerical procedure that is used to interpolate a given set of points.In this thesis, an identification scheme that can be used between aircraft fleets isdesigned to prevent unauthorized aircraft from introducing themselves as `friends` toother aircraft. This scheme can be used as a solution to the identification problem inaviation communication. Our method is a combination of classical encryption methodsand zero knowledge proof methods. The method we recommend is not as complicatedas other ZKP methods using graph isomorphism. Moreover, it is not only available formilitary aircraft. The identification scheme which we use can also be used by othernon-aeronautical systems, eg on IoT devices. Because we do not use time-varying IFFcodes, the cost of implementation is lower than other methods. This also makes theoperational cost lower. It is more reliable for secret listening attacks. Because we usethe ZKP, the attacker cannot capture or manipulate any confidential information.In this method, embedded keys similar to each other with the already agreed similarityratio are distributed to the aircraft in the friendly fleets. The same keys weredistributed to the aircrafts in the same fleet. Thanks to the mathematical modeldesigned the identification scheme provides a method to understand the similarityratio of the keys between the two aircrafts. In this method, both sides (interrogatingand responding) make polynomial interpolation with the values installed or given.Interrogator investigates whether the value calculated with a set of values at a certainpoint is the same as the responder part. When the values taken from responder includesthe one that was calculated after interpolating polynomial, the responder is markedas `friend`. If the set of values doesn't include the value calculated by interrogator,then the responder is marked as `foe`. The Zero Knowledge Proof technique made itpossible to mark an aircarft vehicle `friend` or `foe` without sharing any informationabout their embedded keys.Thanks to this method, the messages of the aircrafts that belong to `friend` categorywill be processed after this communication and the messages of the aircraft marked as`unknown` will be ignored.In general, we have presented a more reliable identification system in this study whichis based on zero knowledge proof and classical encryption methods.The software to be used in this identification model that we have developed can bedealt with in future studies in a way that is in compliance with DO-178B standard.