SOS - Securing Open Skies

Abstract

Automatic Dependent Surveillance -Broadcast (ADS-B) is the next generation communication technology selected for allowing commercial and military aircraft to deliver flight information to both ground base stations and other airplanes. Today, it is already on-board of 80% of commercial aircraft, and it will become mandatory by the 2020 in the US and the EU. ADS-B has been designed without any security consideration -messages are delivered wirelessly in clear text and they are not authenticated. In this paper we propose Securing Open Skies (SOS), a lightweight and standard-compliant framework for securing ADS-B technology wireless communications. SOS leverages the well-known µTESLA protocol, and includes some modifications necessary to deal with the severe bandwidth constraints of the ADS-B communication technology. In addition, SOS is resilient against message injection attacks, by recurring to majority voting techniques applied on central community servers. Overall, SOS emerges as a lightweight security solution, with a limited bandwidth overhead, that does not require any modification to the hardware already deployed. Further, SOS is standard compliant and able to reject active adversaries aiming at disrupting the correct functioning of the communication system. Finally, comparisons against state-of-the-art solutions do show the superior quality and viability of our solution.

Holistic Air Protection Scheme of ADS-B Communication

“…Another scheme based on the TESLA protocol, very similar to [18], is given in [19] and called Securing Open Skies (SOS). The main differences are that messages can be verified in batches, the message digest is set to 128 bits instead of 16, and the design is described in such a way that it is completely compliant with the current standard with respect to packet format and size.…”

“…Consequently, combining ideas of [19] with respect to compatibility and security length on the one hand and [18] regarding the broadcast of security material on the other hand results in an interesting scheme to be used as benchmark for the evaluation of the proposed scheme HAP.…”

“…• Similar as in [19] and according the standard, the first 8 bits of this payload are dedicated to the type of the message. For the type, numbers 25 till 27 and 30 are reserved [25].…”

“…However, even if another input of the hash is found, without knowledge of the private key, the signature cannot be made on any other acceptable input due to the computational hardness of the ECDLP. Note that the output length of the authentication digit in [19] is also set to 128 bits. However, there the impact of a shorter digit is more severe because a successful pre-image attack will allow to create another hash chain, resulting in a complete impersonation attack on an aircraft.…”

“…The performance of HAP is now discussed, using the TESLA based approach [18], [19] as benchmark since this is the only type of scheme currently proposed in literature, which promises some reasonable trade-off between security and performance. Note that from a security point of view, the TESLA based scheme can only reach security level 1 of HAP.…”