The rapid development of advanced computing technologies such as quantum computing imposes new challenges to current wireless security mechanism which is based on cryptographic approaches. To deal with various attacks and realize long-lasting security, we are in urgent need of disruptive security solutions. In this article, novel security transmission paradigms are proposed to approach Shannon's one-time pad perfect secrecy. First, two metrics, termed as Degree-of-Approaching (DoA) and Degree-of-Synchronous-Approaching (DoSA), are developed to characterize the closeness between the achieved security strength and perfect secrecy. These two metrics also serve as a guideline for secure transmission protocol design. After that, we present two paths towards Shannon's one-time pad, i.e., an explicit-encryption based approach and an implicit-encryption based approach. For both of them, we discuss the architecture design, enabling technologies, as well as preliminary performance evaluation results. The techniques presented in this article provide promising security-enhancing solutions for future wireless networks.
The rapid development of advanced computing technologies such as quantum computing imposes new challenges to current wireless security mechanism which is based on cryptographic approaches. To deal with various attacks and realize long-lasting security, we are in urgent need of disruptive security solutions. In this article, novel security transmission paradigms are proposed to approach Shannon's one-time pad perfect secrecy. First, two metrics, termed as Degree-of-Approaching (DoA) and Degree-of-Synchronous-Approaching (DoSA), are developed to characterize the closeness between the achieved security strength and perfect secrecy. These two metrics also serve as a guideline for secure transmission protocol design. After that, we present two paths towards Shannon's one-time pad, i.e., an explicit-encryption based approach and an implicit-encryption based approach. For both of them, we discuss the architecture design, enabling technologies, as well as preliminary performance evaluation results. The techniques presented in this article provide promising security-enhancing solutions for future wireless networks.
In this thesis, a new practical method to realize one-time pad perfect secrecy for wireless \ncommunication is presented. Most commonly used security methods are based on cryp- tographic \ntechniques employed at the upper layers of a wireless network. These methods basically rely on the \ncomputational hardness of some mathematical problems. This com- putational complexity is vulnerable \nin nature due to fast-growing computational power of hardware technology, yet not taking into \naccount the revolution of Quantum computing in further future. Another core problematic issue \nexists in symmetric security systems; there is a deadlock between securing the channel and \nestablishing the shared key. We need the key for securing the channel, on the other hand, for \nsharing the key we need a secure channel. \n \nTo address such vulnerabilities, Physical Layer Security (PLS) has been widely studied in recent \nyears. PLS schemes build on the idea of turning unpredictable and random wire- less channel \ncharacteristics into a source for information-theoretic security. Information- theoretic security \nitself, relies on Shannon’s pioneer work . Shannon, inspired by one-time pad, also known as Vernam \ncipher, theoretically showed that the only unconditional per- fect secrecy system is a one-time pad \nwith a key at least as random as the plaintext, i.e., a system that uses a different random key to \ncipher any new plaintext. In PLS key genera- tion methods, legitimate parties alternately send \nprobe signals and estimate Channel State Information (CSI) of common random channel and then \nconvert enough amount of these estimates to secure shared keys. To achieve perfect secrecy, the key \ngeneration methods must meet the key randomness and Key Generation Rate (KGR) requirements of \ntheir specific cryptographic applications. \n \nIn this research a new practical system for achieving unconditional perfect secrecy is presented. \nOur system uses channel phase as the probing parameter to fully benefit from its uniform \ndistribution over [0, 2π]. It also uses an encryption method based on modulo- \n2π addition of phase values which is the perfect counterpart of XOR addition in binary one-time \npad. Moreover, by intentionally perturbing the wireless channel in vicinity of the transceiver \nantenna based on RF-mirrors structure, it produces different random phase values in each channel \nprobing, much faster than the inherent channel variation would do, resulting in dramatically higher \nKGR than any wide-band PLS scheme presented so far and realizing true perfect secrecy. Most \nimportantly, the focus of this research is a detailed practical algorithm for implementing the \nsystem as well as empirical results which makes \nour system the first channel-phase-based PLS scheme implementation, reported so far.
The advent of quantum computing poses a significant threat to conventional cryptographic schemes, which rely on computational hardness assumptions vulnerable to quantum algorithms. While post-quantum cryptography (PQC) focuses on developing new computationally secure primitives, the ultimate goal of perfect secrecy, rooted in Shannon's information theory, demands a re-evaluation. This paper explores the landscape of information-theoretic security (ITS) in post-quantum regimes, moving beyond the classical Shannon limit. We review foundational concepts of ITS, including the one-time pad and its implications for perfect secrecy, and examine how quantum adversaries challenge these notions. The work delves into various approaches to achieve ITS against quantum attacks, including quantum key distribution (QKD) as a primary example, and investigates the potential for information-theoretic security from classical physical layer properties enhanced by quantum mechanics. We discuss the limitations and practical challenges of implementing such schemes, as well as the theoretical implications. This paper proposes a textit{Hybrid Information-Theoretic and Computationally Secure Architecture (HITCSA)} as a novel framework for integrating robust PQC with information-theoretically secure primitives, providing a comprehensive overview of the theoretical underpinnings and practical considerations for achieving truly secure communication in a quantum-threatened world.
Among the problems to guarantee secrecy for in-transit information, the difficulties involved in renewing cryptographic keys in a secure way using couriers, the perfect secrecy encryption method known as One-Time-Pad (OTP) became almost obsolete. Pure quantum key distribution (QKD) ideally offers security for key distribution and could revive OTP. However, special networks that may need optical fibers, satellite, relay stations, expensive detection equipment compared with telecom technology and the slow protocol offer powerful obstacles for widespread use of QKD. Classical encryption methods flood the secure communication landscape. Many of them rely its security on historical difficulties such as factoring of large numbers - their alleged security sometimes are presented as the difficulty to brake encryption by brute force. The possibility for a mathematical breakthrough that could make factoring trivial are poorly discussed. This work proposes a solution to bring perfect secrecy to in-transit communication and without the above problems. It shows the key distribution scheme (nicknamed KeyBITS Platform) based on classical signals carrying information but that carry with them recordings of quantum noise. Legitimate users start with a shared information of the coding bases used that gives them an information advantage that allows easy signal recovery. The recorded noise protects the legitimate users and block the attacker's access. This shared information is refreshed at the end of each batch of keys sent providing the secret shared information for the next round. With encryption keys distilled from securely transmitted signals at each round OTP can be revived and at fast speeds.
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.
Intrigued by the rapid growth and expand of wireless devices, data security is increasingly playing a significant role in our daily transactions and interactions with different entities. Possible examples, including e-healthcare information and online shopping, are becoming vulnerable due to the intrinsic nature of wireless transmission medium and the widespread open access of wireless links. Traditionally, the communication security is mainly regarded as the tasks at the upper layers of layered protocol stack, security techniques, including personal access control, password protection, and end-to-end encryption, have been widely studied in the open literature. More recently, plenty of research interests have been drawn to the physical layer forms of secrecy. As a new but appealing paradigm at physical layer, physical layer security is based on two pioneering works: (i) Shannon’s information-theoretic formulation and (ii) Wyner’s wiretap formulation. \n \nOn account of the fundamental of physical layer security and the different nature of various wireless network, this dissertation is supposed to further fill the lacking of the existing research outcomes. To be specific, the contributions of this dissertation can be summarized as three-fold:(i) exploration of secrecy metrics to more general fading channels; (ii) characterization a new fading channel model and its reliability and security analysis in digital communication systems; and (iii) investigation of physical layer security over the random multiple-input multiple-output (MIMO) α −μ fading channels. \n \nTaking into account the classic Alice-Bob-Eve wiretap model, the first contribution can be divided into four aspects: (i) we have investigated the secrecy performance over single-input single-output (SISO) α −μ fading channels. The probability of non-zero (PNZ) secrecy capacity and the lower bound of secrecy outage probability (SOP) are derived for the special case when the main channel and wiretap channel undergo the same non-linearity fading parameter, i.e., α. Later on, for the purpose of filling the gap of lacking closed-form expression of SOP in the open literature and extending the obtained results in chapter 2 to the single-input multiple-output (SIMO) α − μ wiretap fading channels, utilizing the fact that the received signal-tonoise ratios (SNRs) at the legitimate receiver and eavesdropper can be approximated as new α −μ distributed random variables (RVs), the SOP metric is therefore derived, and given in terms of the bivariate Fox’s H-function; (ii) the secrecy performance over the Fisher-Snedecor F wiretap fading channels is initially considered. The SOP, PNZ, and ASC are finalized in terms of Meijer’s G-function; (iii) in order to generalize the obtained results over α −μ and Fisher-Snedecor F wiretap fading channels, a more flexible and general fading channel, i.e., Fox’s H-function fading model, are taken into consideration. Both the exact and asymptotic analysis of SOP, PNZ, and average secrecy capacity (ASC), are developed with closed-form expressions; and (iv) finally, motivated by the fact that the mixture gamma (MG) distribution is an appealing tool, which can be used to model the received instantaneous SNRs over wireless fading channels, the secrecy metrics over wiretap fading channels are derived based on the MG approach. \n \nDue to the limited transmission power and communication range, cooperative relays or multi-hop wireless networks are usually regarded as two promising means to address these concerns. Inspired by the obtained results in Chapters 2 and 3, the second main contribution is to propose a novel but simple fading channel model, namely, the cascaded α −μ. This new distribution is advantageous since it encompasses the existing cascaded Rayleigh, cascaded Nakagami-m, and cascaded Weibull with ease. Based on this, both the reliability and secrecy performance of a digital system over cascaded α −μ fading channels are further evaluated. Closed-form expressions of reliability metrics (including amount of fading (AF), outage probability, average channel capacity, and average symbol error probability (ABEP).) and secrecy metrics (including SOP, PNZ, and ASC) are respectively provided. Besides, their asymptotic behaviors are also performed and compared with the exact results. \n \nConsidering the impacts of users’ densities, spatial distribution, and the path-loss exponent on secrecy issue, the third aspect of this thesis is detailed in Chapter 8 as the secrecy investigation of stochastic MIMO system over α −μ wiretap fading channels. Both the stochastic geometry and conventional space-time transmission (STT) scheme are used in the system configuration. The secrecy issue is mathematically evaluated by three metrics, i.e., connection outage, the probability of non-zero secrecy capacity and the ergodic secrecy capacity. Those three metrics are later on derived regarding two ordering scheme, and further compared with Monte-Carlo simulations.
The current research on physical layer security is far from implementations in practical networks, arguably due to impractical assumptions in the literature and the limited applicability of physical layer security. Aiming to reduce the gap between theory and practice, this thesis focuses on wireless physical layer security towards practical assumptions and requirements. In the first half of the thesis, we reduce the dependence of physical layer security on impractical assumptions. The secrecy enhancements and analysis based on impractical assumptions cannot lead to any true guarantee of secrecy in practical networks. The current study of physical layer security was often based on the idealized assumption of perfect channel knowledge on both legitimate users and eavesdroppers. We study the impact of channel estimation errors on secure transmission designs. We investigate the practical scenarios where both the transmitter and the receiver have imperfect channel state information (CSI). Our results show how the optimal transmission design and the achievable throughput vary with the amount of knowledge on the eavesdropper's channel. Apart from the assumption of perfect CSI, the analysis of physical layer security often ideally assumed the number of eavesdropper antennas to be known. We develop an innovative approach to study secure communication systems without knowing the number of eavesdropper antennas by introducing the concept of spatial constraint into physical layer security. That is, the eavesdropper is assumed to have a limited spatial region to place (possibly an infinite number of) antennas. We show that a non-zero secrecy rate is achievable with the help of a friendly jammer, even if the eavesdropper places an infinite number of antennas in its spatial region. In the second half of the thesis, we improve the applicability of physical layer security. The current physical layer security techniques to achieve confidential broadcasting were limited to application in single-cell systems. The primary challenge to achieve confidential broadcasting in the multi-cell network is to deal with not only the inter-cell but also the intra-cell information leakage and interference. To tackle this challenge, we design linear precoders performing confidential broadcasting in multi-cell networks. We optimize the precoder designs to maximize the secrecy sum rate with based on the large-system analysis. Finally, we improve the applicability of physical layer security from a fundamental aspect. The analysis of physical layer security based on the existing secrecy metric was often not applicable in practical networks. We propose new metrics for evaluating the secrecy of transmissions over fading channels to address the practical limitations of using existing secrecy metrics for such evaluations. The first metric establishes a link between the concept of secrecy outage and the eavesdropper's ability to decode confidential messages. The second metric provides an error-probability-based secrecy metric which is often used for the practical implementation of secure wireless systems. The third metric characterizes how much or how fast the confidential information is leaked to the eavesdropper. We show that the proposed secrecy metrics enable one to appropriately design secure communication systems with different views on how secrecy is measured.