Enhancing ADS-B Security through Hybrid Cryptographic and Band-Switching Techniques

Abstract

This thesis presents a comprehensive investigation of unidirectional broadcast communications, with a focus on Automatic Dependent Surveillance-Broadcast (ADS-B) communication in aviation. Following a detailed survey of legacy surveillance systems and the principles of Mode-S Extended Squitter, it identifies the security vulnerabilities in open, unauthenticated ADS-B frames. To establish a reproducible experimental baseline, a low-cost receiver was designed using RTL-SDR and a Raspberry Pi, validating timing, pulse-shape, and framing assumptions and reproducing known attack scenarios. Complementing this, a MATLAB - based signal - generation framework was designed to synthesize fully compliant ADS-B waveforms and adversarial payloads. The core contribution, the Bit-Level Obfuscation with Band-Switching (BLOBS) technique, proposes a methodology involving bit-level scrambling and nanosecond range frequency switching to scramble 112-bit ADS-B messages across multiple channels while preserving backward compatibility with existing ground stations. Prototype implementation on a band-switchable transceiver IC confirmed error free reassembly and decoding, promising significant resilience to selective jamming, spoofing and passive tracking. Beyond aviation, the signal-generation tools and proposed BLOBS technique are generalized for future implementation in other broadcast-based communication schemes. Collectively, these contributions deliver both an open experimental platform and propose a physical-layer defense strategy, charting a clear pathway toward securing next-generation unidirectional broadcast communications without sacrificing their inherent simplicity, low latency, or wide-area coverage.