ADS-B Authentication Compliant with Mode-S Extended Squitter Using PSK Modulation

This work proposes to use Differential 16 Phase-Shift Keying (D16PSK) modulation for embedding a digital signature within Mode-S Extended Squitter (ES) Automatic Dependent Surveillance-Broadcast (ADS-B) messages. The purpose is to provide a security mechanism in order to protect systems against the injection of malicious Hazardously Misleading Information (HMI). The use of digital signatures for ADS-B has been previously analyzed in the literature. Our contribution and focus are devoted to the physical layer used to transmit such a signature. The proposed method generates ADS-B messages compliant with current standards, thus can be interpreted by current equipment. However, only a modified receiver shall be able to extract the embedded signature and authenticate the message. This work describes possible architectures for the ADS-B transmitting and receiving devices. An analysis of the expected maximum range and bit error rate for various PSK modulations is provided. In addition, the use of timestamps to protect against message replays is proposed and studied in the final part of the paper. In summary, this paper proposes a backward compatible way to secure the ADS-B system for the Mode-S ES data link, providing regulatory authorities with the means in case they opt for the use of digital signatures. The proposal is inspired from the idea behind the wireless security encryption method of Nagravision used in the Satellite TV broadcasting.