Abstract RKD (radio-signal key distribution) is a physical method for the secure generation and distribution of cryptographic keys. RKD uses radio signals above 30 MHz to calculate and distribute the keys and is known in the literature under various names, e.g., “physical layer key generation in wireless networks” or “wireless physical layer key agreement.” RKD exploits the unique physical properties of wireless radio channels. The method is based on two fundamental properties of high-frequency transmission: the inherent unpredictability (randomness) of channel properties and the reciprocity of radio transmission between two communication partners.
Abstract RKD (radio-signal key distribution) is a physical method for the secure generation and distribution of cryptographic keys. RKD uses radio signals above 30 MHz to calculate and distribute the keys and is known in the literature under various names, e.g., “physical layer key generation in wireless networks” or “wireless physical layer key agreement.” RKD exploits the unique physical properties of wireless radio channels. The method is based on two fundamental properties of high-frequency transmission: the inherent unpredictability (randomness) of channel properties and the reciprocity of radio transmission between two communication partners.
Due to the broadcast nature of wireless channels, wireless communication is vulnerable to eavesdropping, message modification, and node impersonation. Securing the wireless communication requires the shared secret keys between the communicating entities. Traditional security schemes rely on public key infrastructures and cryptographic algorithms to manage secret keys. Recently, many physical-layer-based methods have been proposed as alternative solutions for key generation in wireless networks. These methods exploit the inherent randomness of the wireless fading channel to generate secret keys while providing information-theoretical security without intensive cryptographic computations. This article provides an overview of the existing PHY-based key generation schemes exploiting the randomness of the wireless channels. Specifically, we first introduce the fundamental and general framework of the PHY-based key generation schemes and then categorize them into two classes: received-signal-strength-based and channel- phase-based protocols. Finally, we present a performance comparison of them in terms of key disagreement probability, key generation rate, key bit randomness, scalability, and implementation issues.
Conventionally, secrecy is achieved using cryptographic techniques beyond the physical layer. Recent studies raise the interest of performing encryption within the physical layer by exploiting some unique features of the physical wireless channel. Following this spirit, we present a novel physical layer encryption (PLE) scheme that randomizes the radio signal using a secret key extracted from the wireless channel under the assumption of channel reciprocity. Specifically, we propose to jointly design the encryption function and the secret-key generation method. On one hand, we establish a sufficient and necessary condition for the encryption function to achieve perfect secrecy. Based on that, several candidate encryption functions are proposed and compared. We show that, given the secret key available to the legitimate users, perfect secrecy can be achieved without compromising the capability of the communication channel. On the other hand, we study the practical design of the secret-key generation method based on the channel reciprocity. We show that, by introducing marginal system overhead, the key agreement between the legitimate users can be done with a high success probability. The performance advantages of the proposed PLE method is verified through comparisons against other existing PLE methods.
In recent years, physical layer security has become one of the core technologies for wireless communication system security. Physical layer encryption is based on the inherent reciprocity, time-varying, spatial uniqueness and unpredictability of wireless communication systems to generate keys, which are naturally unforgeable and steganography-proof. However, the research of physical layer key generation technology also faces many challenges, such as the problem of poor key generation performance due to signal interference, the problem of lower randomness and slower key generation rate in quasi-static channel environment, and the problem of lower key consistency between two legitimate communication parties due to the existence of channel estimation errors; this paper provides a systematic explanation of the traditional model of key generation for wireless channels and a typical solution for this series of problems. In this paper, the traditional model of wireless channel key generation is systematically explained, and the typical solutions to this series of problems are studied, analysed and compared in terms of performance.
A less expensive and more flexible solution to the problem of sharing secret keys between wireless nodes is to use the inherent randomness in the wireless channel between them as the source for extracting bits of the secret key between these nodes. We propose a new secret key distribution approach that utilizes the uniformly distributed phase information of channel responses to extract shared cryptographic keys under narrowband multipath fading models. Compared to existing approaches which only support pair wise key distribution, our scheme is highly scalable and can support efficient group key distribution. Various key distribution schemes are appraised to determine the level of security and connectivity. Simulated results show that key distribution exploiting channel phase has improved resilience against node capture. them as the source for extracting bits of the secret key between these nodes. Shared secret key distribution from channel measurements is an application which benefits from the randomnessof the multipath channel. It would not, for example, work in a truly free-space environment (such as deep space radio links). Secret sharing benefits from: • Reciprocity of the wireless radio channel: The multipath properties of the radio channel (gains, phase shifts, and delays) at any point in time and on any given frequency channel are identical on both directions of the link. • Temporal variations in the radio channel: Over time, the multipath channel changes due to movement of either end of the link, and any motion of people and objects in the environment near the link. An application may specifically request a user to move or shake the wireless device in order to generate more temporal variation. • Spatial variations: The properties of the radio channel are unique to the locations of the two endpoints of the link. An eavesdropper at a third location more than a few wavelengths from either endpoint will measure a different, uncorrelated radio channel. The proposed scheme is more flexible and can be applied in both static and mobile environments. Our scheme introduces phase randomness to bit distribution and removes the reliance on node mobility to obtain high entropy bits. We evaluate the proposed schemes through both analytical and simulation studies. The parameters of the scheme can be selected such that a desired level of key distribution accuracy and reliability is achieved with high efficiency.
Abstract If the security assessments are not trusted, especially in cases of very high data security requirements, physical methods must be used for key generation and distribution, data encryption, and integrity and authenticity procedures. This ensures the confidentiality, integrity, and authenticity of the data against computationally powerful adversaries and mathematical attack methods that are still unknown (unpublished) today. This chapter provides an introduction to these topics, briefly compares mathematical methods, and discusses the generation and distribution of cryptographic keys, as well as QKD (Quantum Key Distribution), RKD (Radio signal Key Distribution), and MKD (Memeory Key Distribution).
Nowadays wireless networks are highly concerned about security. Compared to wireless networks, wired networks are less prone to attacks. The physical layer eavesdropping attack has a significant impact on wireless network security. The use of cryptographic methods at the higher layers of the OSI model is necessary for traditional security in wireless networks. These cryptographic keys can be replaced with key generation at physical layer exploiting the unpredictable channel properties. Current methods for generating wireless keys at the physical layer are examined in this paper. Comprehensive surveys in this regard are conducted of the guiding principles, performance indicators, and key generation process. Techniques for enhancing the effectiveness of key generation are also reviewed. The difficulties of using the strategy in each situation are then discussed, along with key generation applications in diverse situations. The paper ends with several recommendations for future investigations.