Authenticated safety beacons in Vehicular Communication (VC) systems ensure awareness among neighboring vehicles. However, the verification of beacon signatures introduces significant processing overhead for resource-constrained vehicular On-Board Units (OBUs). Even worse in dense neighborhood or when a clogging Denial of Service (DoS) attack is mounted. The OBU would fail to verify for all received (authentic or fictitious) beacons. This could significantly delay the verifications of authentic beacons or even affect the awareness of neighboring vehicle status. In this paper, we propose an efficient cooperative beacon verification scheme leveraging efficient symmetric key based authentication on top of pseudonymous authentication (based on traditional public key cryptography), providing efficient discovery of authentic beacons among a pool of received authentic and fictitious beacons, and can significantly decrease waiting times of beacons in queue before their validations. We show with simulation results that our scheme can guarantee low waiting times for received beacons even in high neighbor density situations and under DoS attacks, under which a traditional scheme would not be workable. rights reserved.

We study the State-Dependent Gaussian Z-Interference Channel (SDG-ZIC), with two senders transmitting two independent messages through a Gaussian Z-interference channel with the same state. Transmitter 1 interferes with receiver 2, while transmitter 2 does not interfere with receiver 1. In addition, both receivers suffer from the same but differently scaled random state sequence, which is non-causally known at both transmitters. As mentioned in [1], the challenge here is to fully cancel differently scaled states at both receivers. Proposing transmission schemes based on nested lattice codes, we show that under some new conditions, the state at both receivers can be fully canceled and the capacity region can be fully achieved.

The security of global navigation satellite systems draws attention increasingly, and authentication mechanisms for civilian services seem very effective in thwarting malicious behavior. For example, the Galileo E1 Open Service introduces navigation message authentication. Authentication, as well as encryption at navigation message or spreading code level, can prevent spoofing attacks, but do not preclude replay attacks. In this work, we consider a type of strong replay attacks, distance-decreasing attacks, against cryptographically protected GNSS signals. Distance-decreasing attack enhance an attacker’s capability of allowing it to mislead the victim receiver that the GNSS signals arrive earlier than true signals. We analyze the instantiation and the effects of the distance-decreasing attacks on unprotected GNSS signals, on navigation message authenticated signals, and on spreading-code encrypted signals. We discuss different strategies that the attacker can adopt to introduce the least bit errors to the re-transmitted signals and avoid being detected at the victim receiver. We provide evaluation results of distance-decreasing attacks on unprotected signals and authenticated navigation message signals, based on different strategies and configurations, and we sketch countermeasures to the different strategies.

The central building block of secure and privacy-preserving Vehicular Communication (VC) systems is a Vehicular Public-Key Infrastructure (VPKI), which provides vehicles with multiple anonymized credentials, termed pseudonyms. These pseudonyms are used to ensure message authenticity and integrity while preserving vehicle (thus passenger) privacy. In the light of emerging large-scale multi-domain VC environments, the efficiency of the VPKI and, more broadly, its scalability are paramount. By the same token, preventing misuse of the credentials, in particular, Sybil-based misbehavior, and managing “honest-but-curious” insiders are other facets of a challenging problem. In this paper, we leverage the state-of-the-art VPKI system and enhance its functionality towards a highly-available, dynamically-scalable, and resilient design; this ensures that the system remains operational in the presence of benign failures or resource depletion attacks, and that it dynamically scales out, or possibly scales in, according to request arrival rates. Our full-blown implementation on the Google Cloud Platform shows that deploying large-scale and efficient VPKI can be cost-effective.

We study the problem of securely estimating the states of an unstable dynamical system subject to non-stochastic disturbances. The estimator obtains all its information through an uncertain channel, which is subject to nonstochastic disturbances as well, and an eavesdropper obtains a disturbed version of the channel inputs through a second uncertain channel. An encoder observes and block encodes the states in such a way that, upon sending the generated codeword, the estimator's error is bounded and a security criterion is satisfied, thereby ensuring that the eavesdropper obtains as little state information as possible. Two security criteria are considered and discussed with the help of a numerical example. A sufficient condition on the uncertain wiretap channel, i.e., the pair formed by the uncertain channel from the encoder to the estimator and the uncertain channel from the encoder to the eavesdropper is derived, which ensures that a bounded estimation error and security are achieved. This condition is also shown to be necessary for a subclass of uncertain wiretap channels. To formulate the condition, the zero-error secrecy capacity of uncertain wiretap channels is introduced, i.e., the maximal rate at which data can be transmitted from the encoder to the estimator in such a way that the eavesdropper is unable to reconstruct the transmitted data. Finally, the zero-error secrecy capacity of uncertain wiretap channels is studied.

Because of the limited satellite visibility, reduced signal reception reliability and constraining spatial geometry, e.g., in urban areas, the development of multi-constellation global navigation satellite systems (GNSS) has gained traction rapidly. GNSS-based applications are expected to handle observations from different navigation systems, e.g., GPS, GLONASS, Bei-Dou and Galileo, in order to improve positioning accuracy and reliability. Furthermore, multi-constellation receivers present an opportunity to better counter spoofing and replaying attacks, leveraging approaches take advantage of the redundant measurements. In particular, cluster-based solution separation algorithm (CSSA) proposes to detect and identify faulty/malicious signals in a single GPS constellation by checking the consistency of receiver positions calculated with different number of satellites. Intuitively, the algorithm targets directly the consequence of spoofing/replaying attacks: the victim receiver position error estimation. It works independently of how the attacks are launched, either through modifying pseudorange measurements or manipulating the navigation messages, without changing the receiver hardware. Multi-constellation GNSS receivers utilize all observations from different navigation systems, there are more than 30 available satellites at each epoch after Galileo and BeiDou systems become fully operational; in other words using abundant redundancy. Therefore, we introduce such a CSSA to a multi-constellation receiver. The work shows that a multi-constellation GNSS receiver equipped with our algorithm works effectively against a strong spoofing/replaying attacker that can manipulate a large number of signals, or even an entire constellation. The results show that CSSA with multi-constellation significantly improves the performance of detecting and identifying the malicious signals; particularly, when the adversary cannot control all the constellations, a multi-constellation receiver can identify the faults even the adversary induces very small errors to pseudorange measurements, comparing with a single constellation receiver. Moreover, when the attacker is powerful to manipulate most of signals of all the constellations, a multi-constellation receiver with CSSA can still detect and identify the faulty signals with high probability when the attacker tries to mislead the victim more than a couple of hundred meters from its true location.

We study, using information-theoretic security methods, the so-called symmetric two-hop channel with an untrusted relay. In this model, a source wants to send its message reliably and securely to the destination through an honest but curious relay. The relay acts as a passive eavesdropper. Our investigation, in line with the relevant literature, seeks to determine what rate, termed secrecy rate, is achievable. To do that, we consider a typical setting, with the destination cooperating with the source, sending a 'scrambling' signal to conceal the message from the relay. To derive the achievable secrecy rate, we propose a novel scheme based on nested lattice codes. We show that our scheme outperforms all existing schemes and it achieves the outer bound for this channel model within 0.33 bits.

Global Navigation Satellite Systems (GNSS) are vulnerable to jamming, spoong and replaying aacks because of their characteristics. Concerns regarding these aacks are being heightened because unmanned and autonomous vehicles become popular recently. Cryptographic methods have been proposed and are to be implemented in the Galileo and the GPS systems to counter spoong aacks. However, replaying aacks could still potentially harm GNSS receivers by bypassing the cryptographic methods. Distance-decreasing aacks is a strong type of replay aacks: it essentially resolves, from the aacker's point of view, the issue of introducing processing delay by implementing two phases: early detection and late commit. is poster analyzes the feasibility of distance-decreasing aacks against the GNSS navigation message authenticated signals and proposes countermeasures.

Radio Tomographic Imaging (RTI) enables novel radio frequency (RF) sensing applications such as intrusion detection systems by observing variations in radio links caused by human actions. RTI applications are, however, severely limited by the requirement to retrofit existing infrastructure with energy-expensive sensors. In this demonstration, we present our ongoing efforts to develop the first battery-free RTI system that operates on minuscule amounts of energy harvested from the ambient environment. Our system eliminates the energy-expensive components employed on state-of-the-art RTI systems achieving two orders of magnitude lower power consumption. Battery-free operation enables a sustainable deployment, as RTI sensors could be deployed for long periods of time with little maintenance effort. Our demonstration showcases an intrusion detection scenario enabled by our system.