An overview of physical-layer security theory for wireless communication is presented, along with a discussion of the potential feasibility to smart cities and potential future research directions. For a long time security at the physical-layer has been neglected in favour of computational methods implemented at the upper-layers of the protocol stack. Upper-layer cryptography techniques use encryption with a shared-key to achieve secrecy. This security is invariably achieved using cryptographic methods. Current encryption methods are deemed to be secure because the level of computational power required to crack the keys is not attainable
using current technology. Nonetheless, the rise of more powerful technologies such as quantum computing may soon challenge this assumption. The computational complexities required to
implement public key encryption prevents low-resource devices from using them. This can have a significant impact on wireless systems for Smart Cities which might be limited in terms of available power or computational overhead.
An overview of physical-layer security theory for wireless communication is presented, along with a discussion of the potential feasibility to smart cities and potential future research directions. For a long time security at the physical-layer has been neglected in favour of computational methods implemented at the upper-layers of the protocol stack. Upper-layer cryptography techniques use encryption with a shared-key to achieve secrecy. This security is invariably achieved using cryptographic methods. Current encryption methods are deemed to be secure because the level of computational power required to crack the keys is not attainable
using current technology. Nonetheless, the rise of more powerful technologies such as quantum computing may soon challenge this assumption. The computational complexities required to
implement public key encryption prevents low-resource devices from using them. This can have a significant impact on wireless systems for Smart Cities which might be limited in terms of available power or computational overhead.
The security of the Internet of Things (IoT) is receiving considerable interest as the low power constraints and complexity features of many IoT devices are limiting the use of conventional cryptographic techniques. This article provides an overview of recent research efforts on alternative approaches for securing IoT wireless communications at the physical layer, specifically the key topics of key generation and physical layer encryption. These schemes can be implemented and are lightweight, and thus offer practical solutions for providing effective IoT wireless security. Future research to make IoT-based physical layer security more robust and pervasive is also covered.
In virtually all communication systems, the issues of authentication, confidentiality, and privacy are handled in the upper layers of the protocol stack using variations of private-key and public-key cryptosystems. These cryptosystems are usually based upon mathematical operations, such as the factorization into prime factors, believed hard to perform for an attacker with limited computational power; hence, we refer to the security provided by these systems as computational security. While computational security has a clear trackrecord of proven effectiveness, it may be difficult to implement in some emerging network architectures. For example, the advent of wireless networks has fostered the development of mobile adhoc networks comprised of many devices with heterogenous capabilities; the wide range of computing power available in the devices makes it difficult to deploy a public-key infrastructure. In contrast with the established practice of computational security, many results from information theory, signal processing, and cryptography suggest that there is much security to be gained by accounting for the imperfections of the physical layer when designing secure systems. For instance, while noise and fading are usually treated as impairments in wireless communications, information-theoretic results show that they can be harnessed to “hide” messages from a potential eavesdropper or authenticate devices, without requiring a shared secret key. Such results, if they can be implemented in a costefficient way without sacrificing much data rate, call for the design of security solutions at the physical layer itself to complement computational security mechanisms.
To ensure confidentiality, today's communications are encrypted under the notion of computational security, using hard mathematical problems to build ciphers that apparently cannot be cracked in a useful time. However, as these constructions are not agnostic to technological advances, some of these problems may be solved efficiently with future technologies, e.g. quantum computing. In wireless networks, physical layer security emerges as a post-quantum security solution that promises to mitigate these threats. This concept of secrecy exploits the physical properties of the wireless channel to encode information so that a certain degree of statistical independence between the message and the cyphertext is observed by the eavesdropper. This notion of secrecy allows building cryptosystems that are agnostic to the computing capabilities of the attacker, being widely accepted as one of the strongest notions of secrecy created so far. The objective of this chapter is to overview the concept of physical layer security and understand how its integration could be done in future wireless networks. For that purpose, the information-theoretical framework grounding the concept is introduced, and some basic design approaches are presented. These include PHY key generation methods, secure beamforming techniques, and cooperative jamming constructions. The mechanisms to enable the integration of these technologies in future 5G and beyond networks are discussed last.
Electromagnetic induction, the earliest form of wireless energy transfer, was demonstrated by Michael Faraday in 1831, happening to be the infancy of radio communication. Since then, this technique in various scales was used for communications, eventually converging to a democratic name "Radio" in the early 1900s as we know it today. Radio frequency or RF communications are collectively and broadly referred to the communication of wireless nature using electromagnetic waves with a frequency of roughly a few kHz to several THz. RF communications are used for several applications ranging from leisure, meteorology, public broadcast, commercial, domestic and defense communications, and so forth. However, when information is communicated, often there is a need to distinguish among the intended receivers and eavesdroppers, for reasons of secrecy, confidentiality, and integrity, like for requirements from personal privacy, till national security. At present, wireless communications are mostly secured in the top level through mathematic encryption - the Advanced Encryption Standard (AES) and the Rivest-Shamir-Adleman (RSA) methods are some examples of this, and in smaller levels by techniques like range limiting, frequency diversity and similar. Anyhow the prominent mode of security is mathematic-based software encryption.Now it is apparent that researchers (ethical or unethical) are working hard like the research community in software encryption to find techniques to crack into the information transmitted. Very often a scenario is encountered such that a transmitted spectrum is recorded and is then cracked over time using several reverse engineering and computational approaches. After all, software encryption is nothing but a complicated mathematical function that, in principle, is always solvable, provided enough time and computational effort is applied to the challenge. This is like eavesdropping an unknown language speaker, recording the conversation, and then transliterating it later with the help of a proficient translator.The current advances in computing and artificial intelligence, like the advent of quantum computing makes this plot worse as computation power and competence is evolving day by day [1-4].An added fortress to wireless communication in the shadow of such an impending vulnerability is hardware security, which is interchangeably called physical layer network security. This is synonymous to adding an extra padlock alongside a combination lock that extends the security over time and effort. Thus, physical layer wireless security is a set of hardware control approaches which makes sure that an effective reception of transmitted data constellation (often software encrypted) could be received in the right format only along pre-defined secure directions or locations. The transmission along all other directions or locations is either scrambled or prevented. This is a relevant concern and is backed by the fact that in a conventional antenna-based transmission, even though the directional gain of the antenna can be controlled, the constellation pattern of transmitted data is distributed in free space almost omnidirectionally around it. Thus, a receiver of adequate sensitivity would be able to record the transmitted data even though it is encrypted mathematically.In this chapter, we broadly classify this concept, discuss several types of reported technologies for physical layer wireless security, and outline their comparisons. Finally, a future perspective of the same is drawn for readers who are interested in this promising research topic.
The open nature of radio propagation enables ubiquitous wireless communication. This allows for seamless data transmission. However, unauthorized users may pose a threat to the security of the data being transmitted to authorized users. This gives rise to network vulnerabilities such as hacking, eavesdropping, and jamming of the transmitted information. Physical layer security (PLS) has been identified as one of the promising security approaches to safeguard the transmission from eavesdroppers in a wireless network. It is an alternative to the computationally demanding and complex cryptographic algorithms and techniques. PLS has continually received exponential research interest owing to the possibility of exploiting the characteristics of the wireless channel. One of the main characteristics includes the random nature of the transmission channel. The aforesaid nature makes it possible for confidential and authentic signal transmission between the sender and the receiver in the physical layer. We start by introducing the basic theories of PLS, including the wiretap channel, information-theoretic security, and a brief discussion of the cryptography security technique. Furthermore, an overview of multiple-input multiple-output (MIMO) communication is provided. The main focus of our review is based on the existing key-less PLS optimization techniques, their limitations, and challenges. The paper also looks into the promising key research areas in addressing these shortfalls. Lastly, a comprehensive overview of some of the recent PLS research in 5G and 6G technologies of wireless communication networks is provided.
Security issues for traditional wireless networks have been considered as a very important research area, and have taken a considerable attention for several years due to the broadcast nature of the wireless medium, which makes attacks more likely to happen than in wireline systems. Most of the studies in this area focus on the security in the higher layers in the protocol stack via the use of cryptography and key management. The main idea of these security approaches is based on the limited computational power of the eavesdroppers. With the advent of the infrastructureless networks such as mobile ad hoc networks (MANETs), further challenges have appeared which make the nodes more vulnerable to attacks. Among these challenges are the absence of centralized hardware for security problems, the multihop routes that the transmitted information should follow, and the power-limited terminals [152]. Therefore, to cope with these limitations, physical layer security (or informationtheoretic security) has gained a considerable attention in the last few years. The goal of physical layer security is to allow the source to confidentially communicate with the legitimate destination, while the eavesdropper cannot interpret the source information, without any assumption for the eavesdropper nodes such as the computational power, or the available information. From an information-theoretic standpoint, the achieved source-destination confidential rate is called the achievable secrecy rate.