A guarantee of everlasting secrecy is of great interest in modern communication systems. Information-theoretic secrecy is a promising method for providing such and has been widely considered. However, the adoption of information-theoretic security has been hampered by the difficulty of guaranteeing the necessary conditions for secrecy to be realized in a wireless communications environment, where the adversary might have a significant (and likely unknown) signal-to-noise ratio (SNR) advantage over the intended recipient. Thus, whereas the wireless communications environment provides opportunities to gain an advantage over the adversary, as has been considered widely in the literature, it is that same environment that challenges its ultimate utility. We review pertinent past and emerging work to address these challenges and provide perspectives on future directions in the field.
A guarantee of everlasting secrecy is of great interest in modern communication systems. Information-theoretic secrecy is a promising method for providing such and has been widely considered. However, the adoption of information-theoretic security has been hampered by the difficulty of guaranteeing the necessary conditions for secrecy to be realized in a wireless communications environment, where the adversary might have a significant (and likely unknown) signal-to-noise ratio (SNR) advantage over the intended recipient. Thus, whereas the wireless communications environment provides opportunities to gain an advantage over the adversary, as has been considered widely in the literature, it is that same environment that challenges its ultimate utility. We review pertinent past and emerging work to address these challenges and provide perspectives on future directions in the field.
Physical layer security, or information-theoretic security, has attracted considerable attention recently, due to its potential to enhance the transmission secrecy of wireless communications. Various secrecy signaling and coding schemes have been designed at the physical layer of wireless systems to guarantee confidentiality against information leakage to unauthorized receivers, among which the strategy based on the idea of node cooperation is promising. This article provides an overview of the recent research on enhancing wireless transmission secrecy via cooperation. We take a signal processing perspective and focus on the secrecy signal design and optimization techniques to increase secrecy performance. We also propose some future research directions on this topic.
Information security has always been a critical issue in wireless networks. Apart from other secure techniques, covert communication emerges as a potential solution to security for wireless networks owing to its high-security level. In covert communication networks, the transmitter hides the transmitted signals into environmental or artificial noise by introducing randomness to avoid detection at the warden. By eliminating the existence of transmitted signals at the warden, information security can be preserved more solidly than other secure transmission techniques, i.e., without noticing the existence. Due to the promising security protection, covert communication has been successfully utilized in tremendous wireless communication scenarios. However, fundamental challenges in its practical implementation still exist, e.g., the effectiveness of randomness utilization, the low signal-to-interference-plus-noise ratio at legitimate users, etc. In this survey, we demonstrate a comprehensive review concentrating on the applications, solutions, and future challenges of covert communications. Specifically, the covert principle and research categories are first introduced. Then, the applications in the networks with different topologies and the effective covert techniques in the existing literature are reviewed. We also discuss the potential implementation of covert communications in future networks and the open challenges.
The past decade has witnessed significant effort towards establishing reliable and information theoretically secure rates in communication networks, taking advantage of the properties of the communication medium. Such efforts include those in the wireless medium where simultaneous transmissions and the ensuing interference can prove advantageous from an information theoretic secrecy point of view. With the goal of obtaining a secrecy rate that scales with transmit power, structured signaling with simultaneous favorable signal alignment at the legitimate receiver(s) and unfavorable signal alignment at the eavesdropper(s) has proven particularly useful in multi-terminal Gaussian channels. Many challenges remain however in realizing the vision of absolute security provided by the wireless physical layer including handling more realistic models. In this paper, we provide a brief overview of the state of the art, the forward look and argue for an additional asset that could be utilized for secrecy, i.e., bidirectional signaling. Taking the bidirectional wiretap channel as an example, Gaussian signaling is demonstrated to be as good as structured signaling from the degrees of freedom point of view, while observed to be performing better with finite transmit power. Moreover, taking bidirectional signals explicitly into account for encoding performs even better and provides a way forward to synergistically combine physical layer based secrecy and encryption.
In this two-part paper, we consider the transmission of confidential data over wireless wiretap channels. The first part presents an information-theoretic problem formulation in which two legitimate partners communicate over a quasi-static fading channel and an eavesdropper observes their transmissions through another independent quasi-static fading channel. We define the secrecy capacity in terms of outage probability and provide a complete characterization of the maximum transmission rate at which the eavesdropper is unable to decode any information. In sharp contrast with known results for Gaussian wiretap channels (without feedback), our contribution shows that in the presence of fading information-theoretic security is achievable even when the eavesdropper has a better average signal-to-noise ratio (SNR) than the legitimate receiver - fading thus turns out to be a friend and not a foe. The issue of imperfect channel state information is also addressed. Practical schemes for wireless information-theoretic security are presented in Part II, which in some cases comes close to the secrecy capacity limits given in this paper.
Secure communication over a wireless channel in the presence of a passive eavesdropper is considered. Our main interest is in the disadvantaged wireless environment, where the channel from the transmitter Alice to the eavesdropper Eve is (possibly much) better than that from Alice to Bob, hence making information-theoretic secrecy challenging. We present a method to exploit inherent vulnerabilities of the eavesdropper's receiver through the use of “cheap” cryptographically-secure key-bits, which only need be kept secret from Eve for the (short) transmission period of the message, to obtain information-theoretic (i.e. everlasting) secret bits at Bob. In particular, based on an ephemeral cryptographic key pre-shared between Alice and Bob, a random jamming signal with large variations is added to each symbol. The legitimate receiver Bob uses the key to subtract the jamming signal immediately, while Eve is forced to perform the inherently nonlinear operation of recording the signal; when Eve then obtains the key, which we assume pessimistically (for Alice) happens right after message transmission, Eve can then immediately subtract the jamming signal from the recorded signal. But, because of the intervening non-linear operation in Eve's receiver and the non-commutativity of nonlinear operations, Bob's channel and Eve's channel have different achievable rates and information-theoretic secrecy can be obtained, hence achieving the goal of converting the vulnerable cryptographic secret key into information-theoretic secure bits. The achievable secrecy rates for different settings are evaluated. Among other results, it is shown that, even when the eavesdropper has perfect access to the output of the transmitter (albeit through an imperfect analog-to-digital converter), the method can still achieve a positive secrecy rate.
Information theoretic approaches to security have been examined as a promising complement to current cryptographic techniques. Such information theoretic approaches establish reliable communication and data confidentiality directly at the physical layer of a communication network by taking the properties of the noisy channel into account leading to unconditional security regardless of the computational capabilities of eavesdroppers. The provision of accurate channel state information is a major challenge particularly in wireless communication systems, especially information about the channels to eavesdroppers. In addition, there might be malevolent adversaries who jam or influence the channel of the legitimate users. This paper surveys different models for secure communication under channel uncertainty and adversarial attacks and reviews the corresponding secrecy capacity results, which characterize the maximum rate at which information can be sent to legitimate receivers while being kept perfectly security from eavesdroppers.