Authenticating DME Data and Airplane Communication
Distance measuring equipment (DME) is a form of navigation that uses land-based transponders to measure distance by timing propogation delay. First, the airplane interrogates the DME by sending several pulse pairs. The DME responds with pulse pairs after a delay. The two way interrogation provides the airplane with its distance from the specific DME. From this information, the airplane can determine its location. This radio navigation system is typically used on airplanes as a secondary form of radar to complement GPS and is constantly discussed as a form of alternate navigation because it has signals stronger than GPS.
The security problem with DME is that there is no form of authentication between the airplane and the DME. This means the airplane cannot confirm that the messages the airplane receives actually originate from the DME. It is possible to spoof the DME's message and provide incorrect navigation information to the airplane. We provide an approach using cryptography to solve this problem.
Our work: In the report below, we provide 2 DME authentication protocols. The first scheme solely uses signatures and is simpler but requires more bits for authentication. The other scheme uses message authenication codes, which provides the same level of security as the first scheme but with less authentication bits. However, it is more difficult to implement. Both schemes require little additional equipment and minor changes. The specific details of the schemes are described in the writeup below.Full Report: .pdf
Some of the source code for the project has been included below. It is an implementation of the second scheme (MAC scheme) described above.
Source Code: .zip