A Backwards Compatible Approach to Authenticate Automatic Identification System Messages

Since the Automatic Identification System (AIS) has been introduced in 2002, it has become a backbone of maritime navigation to prevent collisions with other vessels. All larger ships are equipped with transponders that send and receive information about nearby vessels, giving bridge crew a situational awareness picture of their immediate vicinity and allowing a broad range of services to receive information about worldwide vessel movements. However, despite its ubiquity, the system itself operates virtually unsecured. Essentially, despite relying on inherently insecure channels and broadcasts, authenticity of messages is not questioned in current systems, making the system vulnerable to spoofing attacks. This paper introduces several backwards compatible signature schemes and compares them concerning their applicability. The proposed solutions all provide means to secure the channels in use against spoofing attacks and at the same time solve current issues concerning the validation of messages, securing AIS as a whole without breaking established implementations.