Physical−Layer Integrity for Wireless Messages
Nils Ole Tippenhauer‚ Kasper Bonne Rasmussen and Srdjan Capkun
In this work, we discuss physical layer message manipulation attacks, in which an attacker changes physical-layer properties of an original wireless message. Instead of targeting the data content of the message, those attacks target message properties such as time-of-arrival, signal strength, angle-of-arrival, and others. As such attacks do not change the data content, they do not violate the message’s data integrity. Instead, we introduce the notion of physical-layer message integrity (PMI), that describes the absence of manipulations for physical-layer message characteristics. Among the different physical-layer characteristics, we focus on delay attacks in which an attacker delays a message sent from victim A to a nearby victim B. Such attacks can be used on time-synchronization, distance measurement, and other time-sensitive measurements such as phase measurements in power grids. In that context, we speak of message temporal integrity (MTI) as characteristic targeted by the attack. Informally, MTI is preserved if the message is neither advanced nor delayed in transmission. We discuss how to detect attacks on MTI, and propose a message temporal integrity protocol based on special message encoding, modulation, and detection.