Security of the ADS-B system in heavy multipath propagation environments

Implementation of the ADS-B system for identification and localization of airplanes has presented a number of technological and regulatory challenges. The system is based on an automatic and continuous broadcasting mechanism of the location, speed and identification of the airplane and together with the traditional radar systems brings better capabilities to air traffic management. Unfortunately, the system also has its flaws in the form of security vulnerabilities. The paper focuses on presenting these vulnerabilities which stem from the system's lack of cryptographic and authentication procedures. Moreover, the existing mitigating techniques are presented and analyzed in new operating environments with strong multipath signal propagation. The current mitigation techniques might not be sufficiently effective in these non-line-of-sight; urban or mountainous low-altitude environments which present a serious security issue. The disparity of the line-of-sight and non-line-of-sight channels is presented for being the main factor when differentiating between the two operational environments. The system is already used with helicopters which operate in such non-line-of-sight environments and, in future, it may be even used with unmanned aircraft. For this purpose, the potential vulnerabilities of the current ADS-B implementation are presented and solutions are proposed based on signal propagation modeling and good ground-station infrastructure.