Introduction/purpose: The paper provides a review of recent research in the field of GPS and ADS-B spoofing. Systems that rely on satellite positioning technology can be targeted by spoofing in order to generate incorrect positioning/timing, which is accomplished by inserting false signals into the "victim's" receiver. Attackers try to insert false positioning information into systems that, for example, provide navigation of airplanes or drones for the purpose of hijacking or distracting security/safety in airspace surveillance. New concepts of navigation and ATC will thus be necessary. Methods: Using a scientific approach, the paper gives an evaluation of GPS and ADS-B spoofing/antispoofing and how spoofing affects the cyber security of aviation systems. Results: Based on the methodological analysis used, the importance of studying spoofing/anti-spoofing in aviation is shown. Conclusion: Although spoofing in aviation is only a potential threat, its technical feasibility is realistic and its potential is considerable; it becomes more flexible and cheaper due to very rapid advancement of SDR technologies. The real risk, in the time to come, are potential spoofing attacks that could occur from the air, using drones. However, aircraft systems are not exposed to spoofing without any defense; receivers can detect it by applying various anti-spufing techniques. Also, pilots are able to detect and solve problems at every stage of the flight. However, due to a possibility of more sophisticated spoofing attacks, international organizations such as ICAO are proactively working to increase GPS and ADS-B systems robustness on spoofing.

Automatic Dependent Surveillance-Broadcast (ADS-B) is a multiparameter surveillance system designed to improve key segments of air traffic: enabling real-time surveillance, raising safety and efficiency levels, and improving flight information and weather services. ADS-B consists of two subsystems, ADS-B Out and ADS-B In. Although only a complete system, ADS-B In/Out provides numerous benefits (additional situational awareness, more efficient oceanic routing, etc.) FAA and EASA only require ADS-B Out (by January and June 2020, respectively), whereby ADS-B In remains optional. Because of its many advantages, ADS-B In/Out will be popular, but there are some weaknesses, which are primarily related to its cyber vulnerabilities due to insufficient authentication and encryption in the applied protocol. In this paper, an overview of the ADS-B system is presented as an aid to understanding the security problems and the different ways of potential attack. In addition, this review deals with the current state of ADS-B deployment and its future perspective and challenges.

SAJBER BEZBEDNOST U AVIJACIJI U eri informacionih i komunikacionih tehnologija, funkcionisanje društva i privrede, pa tako i avio industrije, bazira se na međusobnom povezivanjuračunarskih sistema, koji se koriste za upravljanje raznim operacijama u vazduhoplovstvu. Ovo povezivanje, s jedne strane, omogućava brojne operativne benefite, dok s druge, infrastrukturni sistemi postaju "ranjivi" na različite sajber napade, koji se mogu ostvariti preko različitih sistema, platformi i tehnologija. Ustanovljeno je da su sajber pretnje u porastu, da su dinamične i nepredvidive, a koriste ih tzv. sajber teroristi s ciljem ostvarivanja različitih oštećenja u vazduhoplovnom sistemu, i to svih njegovihdelova, od sistema kontrole letenja, preko aviona i aviokompanija, do aerodroma i pasoške/carinske kontrole. Iako je prema proceni International Civil Aviation Organisation, rizik od uspešnog terorističkog sajber napada sa gubitkom ljudskih života, u odnosu na druge oblike terorizma, relativno nizak, činjenica je da sajber pretnje mogu imati veliki uticaj na bezbednost, operativni i finansijski integritet, kao i ugled avio sektora u celini. Najskorije, uočeni su brojni slučajevi narušavanja operativnosti velikih aviokompanija izazvanih sajberincidentima, koji, naizgled malog obima, a s obzirom na njihovu ulogu u avio procesima i tendenciju porasta, mogu imati daleko šire i ozbiljnije posledice. U tom kontekstu, u ovom radu bavimo se nekim od glavnih pitanja sajber bezbednosti u avijaciji, kao što su razumevanje i definisanje bezbednosnih sajber pretnji, s naročitim osvrtom na poznate primere sa kojima se danas suočava avijacija, ilustrujući tako rasprostranjenost sajber incidenata i uticaj koji imaju na avijaciju, kao i relevatnost ovog rada.

The present paper presents the aeroacoustic calculation methodology for the H-Darrieus wind turbine. The CFD analysis, for different wind turbine blades? angles of attack, coupled with the noise analysis, based on Lighthill and Prudmann models is performed. This type of turbine is of particular interest since it is insensitive to wind direction and can be used in urban areas. In this study commercial software, ANSYS is used for CFD and aeroacoustic analysis. The required turbulent flow field is calculated based on the standard k-? model, and reequired model constants are obtained experimentally in a low-Mach number wind tunnel. The noise levels generated by operating turbine are calculated based on Lighthill and Proudman's aeroacoustic theories. It was found that the methodology presented can be efficiently used in noise analysis of vertical axes wind turbines and due to recent strict noise regulations has to be deployed at the early design stages.

Aircraft systems that rely on satellite positioning technology, such as GNSS and ADS-B, can be the target of a spoofing attack - a sophisticated and very dangerous form of radio frequency interference in which false signals are inserted into the "victim's" receiver for incorrect positioning or timing. Although spoofing in civil aviation is a potential threat, its technical feasibility is realistic, and the application of spoofing is becoming more flexible due to the very rapid progress of cheap SDR platforms. In particular, the potential risk is posed by potential air strikes, using unmanned aerial vehicles/drones, for the purpose of hijacking or distracting security in airspace surveillance. However, aviation is not ruthlessly exposed to spoofing attacks without any defense; by applying certain methods/techniques, spoofing can be mitigated in the GNSS receiver. Also, pilots are trained to detect and solve problems at every stage of the flight. Due to more sophisticated forms of terrorist attacks are possible, international organizations, such as ICAO and EUROCA, are proactively working to increase the robustness of the GNSS and ADS-B systems to spoofing. Given the importance of the topic and the fact that spoofing/antispuffing testing has certain limitations, consideration of the specifics and different scenarios of these attacks are very important in the development of new methods for their mitigation and detection. This paper focuses on spoofing/antispuffing of GNSS and ABS-B systems in civil aviation and provides an overview of the latest research in these areas.