Jamming-resistant communication is crucial for safety-critical applications such as emergency alert broadcasts or the dissemination of navigation signals in adversarial settings. In such applications, mission-critical messages are broadcast to a large and unknown number of (potentially untrusted) receivers that rely on the availability, integrity, and authenticity of the messages; here, availability primarily refers to the ability to communicate in the presence of jamming. Common techniques to counter jamming-based denial-of-service attacks such as Frequency Hopping (FH) and Direct Sequence Spread Spectrum (DSSS) cannot be applied in such settings because they depend on secret pairwise or group keys shared between the sender and the receivers before the communication. This dependency entails serious or unsolvable scalability and keysetup problems or weak jamming-resistance (a single malicious receiver can compromise the whole system). As a solution, in this work, we propose uncoordinated spread spectrum techniques that enable anti-jamming broadcast communication without shared secrets. Uncoordinated spread spectrum techniques can handle an unlimited amount of (malicious) receivers. We present two instances (Uncoordinated FH and Uncoordinated DSSS) and analyze differences in their performance as well as their combination. We further discuss the applications of these techniques to anti-jamming navigation broadcast, bootstrapping of coordinated spread spectrum communication, and anti-jamming emergency alerts.

An integral part of most security- and safety-critical applications is a dependable and timely alarm notification. However, owing to the resource constraints of wireless sensor nodes (i.e., their limited power and spectral diversity), ensuring a timely and jamming-resistant delivery of alarm messages in applications that rely on wireless sensor networks is a challenging task. With current alarm forwarding schemes, blocking of an alarm by jamming is straightforward and jamming is very likely to remain unnoticed. In this work, we propose a novel jamming detection scheme as a solution to this problem. Our scheme is able to identify the cause of bit errors for individual packets by looking at the received signal strength during the reception of these bits and is well-suited for the protection of reactive alarm systems with very low network traffic. We present three different techniques for the identification of bit errors based on: predetermined knowledge, error correcting codes, and limited node wiring. We perform a detailed evaluation of the proposed solution and validate our findings experimentally with Chipcon CC1000 radios. The results show that our solution effectively detects sophisticated jamming attacks that cannot be detected with existing techniques and enables the formation of robust sensor networks for dependable delivery of alarm notifications. Our scheme also meets the high demands on the energy efficiency of reactive surveillance applications as it can operate without introducing additional wireless network traffic.

We address the problem of jamming-resistant communication in scenarios in which the communicating parties do not share secret keys. This includes scenarios where the communicating parties are not known in advance or where not all parties can be trusted (e.g., jamming-resistant key establishment or anti-jamming broadcast to a large set of unknown receivers). In these cases, the deployment of shared secret keys is unrealistic, and therefore this problem cannot be solved using existing anti-jamming solutions like FHSS and DSSS that depend on pre-shared keys. Recently, a solution to this problem has been proposed that introduces Uncoordinated Frequency Hopping (UFH), a new spread-spectrum anti-jamming technique that does not rely on secret keys. In this work, we investigate the efficiency of UFH-based communication: we identify optimal strategies for the UFH frequency channel selection and we propose a set of new UFH-based anti-jamming schemes that, compared to the original UFH proposal, reduce the communication latency up to one-half (i.e., increase UFH communication throughput up to two times).

We consider the following problem: how can two devices that do not share any secrets establish a shared secret key over a wireless radio channel in the presence of a communication jammer? An inherent challenge in solving this problem is that known anti-jamming techniques (e.g.,frequency hopping or direct-sequence spread spectrum) which should support device communication during the key establishment require that the devices share a secret spreading key (or code) prior to the start of their communication. This requirement creates a circular dependency between anti-jamming spread-spectrum communication and key establishment, which has so far not been addressed. In this work, we propose an Uncoordinated Frequency Hopping (UFH) scheme that breaks this dependencyand enables key establishment in the presence of a communication jammer. We perform a detailed analysis of our UFH scheme and show its feasibility, both in terms of execution time and resource requirements.