Metasurfaces enable controllable manipulation of electromagnetic waves and have been shown to be valuable for wireless communications in many diverse ways. In this paper, we explore the notion that these useful components could also provide opportunities for a malicious agent. In particular, we define and experimentally demonstrate for the first time a “MetaSurface-in-the-Middle” (MSITM) attack. In this attack, the adversary Eve places a metasurface in the path of a directive transmission between Alice and Bob and targets to re-direct a portion of the signal towards herself, without being detected. Specifically, we show how Eve can design a metasurface that induces abrupt phase changes at the interface of the metasurface to controllably diffract directional links and establish furtive eavesdropping links. We explore the theoretical foundations of the MSITM attack and demonstrate that an effective metasurface can be prototyped in under 5 min at a minimal cost. We experimentally demonstrate the attack in a THz time-domain system and perform a set of over-the-air experiments. Our results indicate that the MSITM attack yields an acute vulnerability that can significantly reduce empirical secrecy capacity while leaving a minimal energy footprint, making the attack challenging to detect.

Frequency hopping (FH) is an effective distributed blind rendezvous approach used by secondary users (SUs) in dynamic spectrum access (DSA) networks to establish communication links. Several “quorum-based” FH approaches have been proposed in the literature to enable systematic time-asynchronous rendezvous with deterministic guarantees and without requiring role pre-assignment. This paper is concerned with securing such combinatorial FH rendezvous approaches against insider jamming attacks. We develop QUANTA, a Nested QUorum-based ANTi-jamming recursive game-theoretic rendezvous framework to analyze the interactions between a pair of legitimate SUs, who are trying to rendezvous, and a compromised SU, acting as a jammer, in a multi-channel DSA system.

Metasurfaces enable controllable manipulation of electromagnetic waves and have been shown to improve wireless communications in many diverse ways. In this paper, we define and experimentally demonstrate for the first time a "MetaSurface-in-the-Middle'' (MSITM) attack. In this attack, the adversary Eve places a metasurface in the path of a directive transmission between Alice and Bob and targets to re-direct a portion of the signal towards herself, without being detected. In particular, we show how Eve can design a metasurface that induces abrupt phase changes at the interface of the metasurface to controllably diffract directional links and establish furtive eavesdropping links. We explore the theoretical foundations of the MSITM attack and demonstrate that an effective metasurface can be prototyped in under 5 min at the cost of several cents. We experimentally demonstrate the attack in a THz time-domain system and perform a set of over-the-air experiments. Our results indicate that the MSITM attack yields an acute vulnerability that can significantly reduce empirical secrecy capacity while leaving a minimal energy footprint, making the attack challenging to detect.

Metasurfaces enable controllable manipulation of electromagnetic waves and have been shown to improve wireless communications in many diverse ways. Investigating adversarial metasurfaces, we define and experimentally demonstrate for the first time a "MetaSurface-in-the-Middle'' (MSITM) attack in our paper \citeshaikhanov2022MSITM. In the attack, the adversary Eve places a metasurface in the path of a directive transmission between Alice and Bob and targets to re-direct a portion of the signal towards herself, without being detected. Here, we demonstrate the rapid fabrication of the MSITM employing only standard office supplies such as a printer, paper, foil, and laminator. We show that an effective metasurface can be prototyped in under $5$ min at the cost of several cents. We also demo the attack implementation in the THz network, presenting a video of the MSITM attacker establishing a diffractive eavesdropping link while maintaining the legitimate Alice-Bob link. Our results indicate that the attack yields an acute eavesdropping vulnerability while leaving a minimal energy footprint, making the attack challenging to detect.

Channel bonding is one promising approach to cope with rising WLAN data demand, given scarce spectrum resources. An access point (AP) can aggregate multiple contiguous channels to satisfy demand. We discuss how to optimally utilize available frequency bands under uncertainty in AP demands using two stochastic optimization frameworks: a static scheme which minimizes the total occupied bandwidth while satisfying the demand of each AP with probability at least β, and an adaptive scheme that allows adaptability of the bandwidth allocation in response to the AP demand variations. Given its complexity, we propose a novel framework to solve the adaptive stochastic optimization problem efficiently. The proposed framework exploits the special structure of the problem through decomposition into two subproblems. A particle swarm optimization (PSO)-based algorithm is tailored to the first-stage problem in order to obtain good solutions. The second-stage problem is further decomposed into several subproblems that can be solved independently in parallel. Our numerical results (i) demonstrate the advantages of stochastic compared to deterministic allocation, (ii) illustrate that the proposed framework reaches the optimal solution for the two-stage problem in few iterations, and (iii) explain the bandwidth-user satisfaction trade-off provided by the adaptive allocation approach.