Visible Light Communication (VLC) is a wireless technology that exploits Light Emitting Diodes (LEDs) for both, illumination and data communication. A major challenge is that this system is vulnerable to passive attacks due to the broadcast nature of wireless networks. In this paper, an efficient and lightweight cipher scheme for VLC systems is proposed at the physical layer. Unlike previous schemes in the literature, the proposed one-round scheme utilizes simple substitution and phase shuffling operations to secure the underlying Orthogonal Frequency Division Multiplexing (OFDM) symbols. A dynamic key derivation scheme that benefits from the dynamic properties of VLC channels is also proposed. Experimental simulations and cryptanalysis show that the proposed solution strikes a good balance between performance and security robustness.

Device-to-Device (D2D) communication is one of the key components of 4G/5G mobile networks since it enhances network capacity and enables support for public applications. On the other hand, device authentication in D2D is an inherent problem since devices connect and leave the network frequently and freely. Recently, "3rd Generation Partnership Project (3GPP)" has adopted the Authentication Key Agreement (AKA) protocol for 5G New Radio (NR) networks, where the Home Network (HN) first authenticates the User Equipment (UE) and then produces sessions keys. However, in D2D communication, data is directly conveyed between communicating entities (independently from the HN), which makes the AKA protocol not very suited for this technology. In this paper, we propose a new framework based on Physical Layer Security (PLS) that targets device authentication and key establishment in D2D/5G communication systems. The proposed protocol uses common channel characteristics and asymmetric cryptography to ensure legitimate authentication, without relying on the core network. Finally, security and performance analysis are presented to prove the proposed scheme's efficiency and immunity against different types of authentication attacks.

Authentication is critical for any digital system as it represents the first step towards accessing data and resources. Authentication of entities, especially devices in the Internet-of-Things (IoT) system, is one of the most important security challenges that needs to be addressed; otherwise, it will hinder the deployment of IoT applications. The most widely used authentication mechanisms in IoT are based on one-factor cryptographic techniques. These techniques are often not sufficient in the context of IoT due to the limited computational power of IoT devices and the severity of security concerns, especially that these devices are physically not well protected. Consequently, any weakness in the identification/authentication schemes would allow a compromised entity to perform dangerous attacks. To overcome the above-mentioned limitations and achieve high authentication accuracy, we propose an efficient two-factor lightweight mutual authentication scheme for IoT entities, which can be deployed at various levels; device, control, aggregation node, gateway, and server. The first factor is based on a cryptographic protocol which employs a configurable Physically Unclonable Function (PUF) along with a nonce extracted from the physical channel. The second factor is an entity-based fingerprint that uses specific information (i.e., features that can be extracted from various layers of the communication protocol) to construct a unique fingerprint for each entity. The proposed scheme is designed to require the minimum possible overhead in terms of computation and communication overhead, and ensure maximum security resilience against authentication attacks.

Physical layer (PHY) security has emerged as a promising methodology for securing current and future networks that employ orthogonal frequency-division multiplexing (OFDM) technology. OFDM is the basic building block for multicarrier modulation in most contemporary networks such as vehicular ad hoc networks, Internet of Things (IoT), as well as 4G/5G systems. Most existing OFDM-based security solutions lack the notion of secrecy and dynamicity when combining a secret key with random information extracted from the physical channel. Yet, some solutions perform encryption preinverse fast Fourier transform and some postinverse fast Fourier transform, without clear guidelines concerning the impact on performance and security. In this paper, OFDM-based encryption schemes at the PHY are investigated, analyzed, and weaknesses are identified. It is shown that encryption in the frequency domain slightly mitigates the effects of channel fading and improves the bit error-rate performance. On the other hand, time-domain encryption is shown to be more secure. Furthermore, a dynamic secret key approach that enhances the security level of OFDM-based encryption schemes, in addition to a new technique for updating cipher primitives for input OFDM symbols or frames, are proposed. These schemes are shown to strike a good balance between performance and security robustness as demonstrated through experimental simulations.

Recently, physical layer security has emerged as a promising security scheme for wireless networks, in contrast to traditional solutions that mainly rely on upper network layers. As such, several physical layer encryption algorithms that benefit from the random characteristics of physical channels have appeared in the literature. However, the majority of these schemes lack the notion of secrecy and dynamicity. In this paper, we focus on enhancing the physical layer encryption for wireless machine-to-machine devices, which share the same channel, with the aim of striking a good balance between performance and security robustness. The main idea is to perform encryption at the physical layer after symbol modulation. The cipher scheme is based on one round and one operation that reduces the encryption overhead in terms of latency and required resources. Furthermore, we propose a dynamic key approach that combines a pre-shared/stored secret key with a dynamic nonce extracted from the channel information to generate a dynamic key. The main advantage of the dynamic key approach is that it achieves a high-security level with minimal overhead. The dynamic key can be changed frequently upon any change in channel parameters or upon starting a new session. In addition to data encryption, a preamble encryption scheme is also proposed to prevent unauthorized synchronization or channel estimation by illegitimate users. Finally, security and performance analyses are performed to demonstrate the validity, efficiency and robustness of the proposed approach.

Multipath TCP (MP-TCP) has been introduced as an extension to the legacy TCP transport protocol to support communication through multiple paths under a single connection session. The target is to improve both resource utilization and connection robustness. Several congestion control algorithms (CCAs) have emerged in the literature to adapt subflow rates to congestion conditions on the various paths without negatively impacting competing single-path TCP sources. The challenge is to provide a trade-off among three factors, namely, fairness, responsiveness, and window oscillation. In this paper, we propose a new fairness-based CCA (FCCA) based on the fluid model that improves fairness without degrading the other two metrics. The FCCA tracks the performance on each route and dynamically adapts the respective congestion windows, enhancing the overall performance. The proposed algorithm is implemented in a Linux kernel. Simulation results demonstrate that FCCA is capable of achieving almost maximal fairness (98%) while maintaining responsiveness, unlike existing CCAs.