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Communications on Applied Electronics

Channel-based Secret Key Establishment for FDD Wireless Communication Systems

Ali M.

Published Nov 29, 2017• 15 citations
Publisher

Abstract

Most of current research on channel-based key generation focused on a time division duplex (TDD) system as the channel reciprocity factor applied directly to the generation of a secret key.However, most of commercial cellular systems rely on a frequency division duplex (FDD) mode.In this paper, we study the utilization of the uplink and downlink of FDD systems for the generation of common secret key between two users in the presents of inactive eavesdropper.The clue of our work is to explore the fading gain of the wireless channel between two users to generate a symmetric key.We develop the upper bound of the generation rate for shared key of the suggested mechanism and give numerical examples to show the performance of our suggested approach.

DOI
10.5120/cae2017652715

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Most of current research on channel-based key generation focused on a time division duplex (TDD) system as the channel reciprocity factor applied directly to the generation of a secret key.However, most of commercial cellular systems rely on a frequency division duplex (FDD) mode.In this paper, we study the utilization of the uplink and downlink of FDD systems for the generation of common secret key between two users in the presents of inactive eavesdropper.The clue of our work is to explore the fading gain of the wireless channel between two users to generate a symmetric key.We develop the upper bound of the generation rate for shared key of the suggested mechanism and give numerical examples to show the performance of our suggested approach.
Summary Most recent research on channel‐based key generation oriented to time division duplex system because the channel reciprocity feature is applied directly for secret key generation. Most of commercial cellular systems depend on frequency division duplex (FDD) systems. In this paper, we investigate the impact of uplink and downlink of FDD systems for the generation of shared secret keys between two parties in the presents of passive eavesdropper. In addition, we are considering improving the rate of the secret key for wireless communication in FDD mode. The main idea is to use the fading coefficient of the channels between the relay and other parties as an additional random common source for the secret key generation. Also, explore the using of channel estimation techniques to reduce the channel training sequence and study its effect on the generation of shared key for wireless communications in FDD mode. We derive the upper bound of the generated shared key rate for four scenarios and give numerical examples to reveal the performance of our suggested improvement approaches.
Channel reciprocity is an inherent feature of time division duplex (TDD) system while in frequency division duplex (FDD) system it is limited due to different frequencies being used for the uplink and the downlink. As a consequence, channel reciprocity-based secret generating methods used in TDD systems cannot be applied directly to FDD systems. In this paper, we present a novel secret key generation method for FDD system, for which the communication pair estimate the channel state information (CSI) of the same time in the uplink by a specially designed forwarding strategy and generate the secret key from the CSI estimates. Numerical simulations are implemented to verify the effectiveness of the proposed method.
Most of the current research on generating a secret key from wireless fading channels relies on the channel reciprocity feature of the time division duplex link between legitimate entities so that they can acquire related information from the joint wireless connection. This paper investigates the challenge of generating a shared secret key in frequency division duplex communication systems, in which there is no reciprocity between the two nodes, in the presence of an active opponent. We suggest a key generation algorithm that depends on the product of two fading coefficients. We additionally look at the effects of an interfering adversary on the suggested key establishment scheme and solve the problem of evaluating the key rate for a scheme depending on virtual channel gain. We illustrate an adversary model using an optimal attacking strategy to minimize the rate of generating a shared secret key for our suggested algorithm. Additionally, we identify the suitable channel conditions for the non‐zero rate in the existence of an interfering adversary using simulation results.
Physical Layer Secret Key Generation (PLSKG), which utilizes wireless channel reciprocity, is increasingly adopted to secure wireless communications. In Time Division Duplexing (TDD) systems, the inherent channel reciprocity facilitates the generation of cryptographic keys without requiring a key exchange process. Conversely, Frequency Division Duplexing (FDD) systems present greater challenges for key generation due to the use of distinct frequency bands for uplink and downlink, resulting in differing frequency responses. In this paper, we address this challenge by modeling the channel along with connecting cables as a two-port network and utilizing the reciprocity principles applicable to such networks within the same frequency range. For key generation, we construct the channel profile for each FDD band by utilizing the amplitude of the bidirectional scattering parameters S12and S21in two closely spaced FDD bands, thereby ensuring the required reciprocity in FDD systems. To assess the practicality of the proposed scheme, we analyze its performance across various indoor scenarios and compare it with other key generation schemes using multiple performance indicators. The comparative results confirm the feasibility and effectiveness of our scheme in terms of randomness and key disagreement ratio.
Key establishment method based on channel reciprocity for time division duplex (TDD) system has earned a vital consideration in the majority of recent research.While most of the cellular systems rely on frequency division duplex (FDD) systems, especially the 5G network, which is not characterized by the channel reciprocity feature.This paper realizes the generation of a group secret key for multi-terminals communicated through a wireless network in FDD mode, by utilizing the nature of the physical layer for the wireless links between them.I consider a new group key generation approach, which using bitwise XOR with a modified pairwise secret key generation approach not based on the channel reciprocity feature.Precisely, this multi-node secret key agreement technique designed for three wireless network topologies: 1) the triangle topology, 2) the multi-terminal star topology, and 3) the multi-node chain topology.Three multi-node secret key agreement protocols suggest for these wireless communication topologies in FDD mode, respectively.I determine the upper bound for the generation rate of the secret key shared among multi-node, for the three multi-terminals topologies, and give numerical cases to expose the achievement of my offered technique.
Physical layer-based key generation encounters the reciprocity bottleneck when applied in frequency-division duplexing (FDD) systems. This letter constructs the reciprocal channel characteristics of the uplink and downlink transmissions for key generation in FDD systems. The frequency dependence of propagation characteristics in both large-scale fading and small-scale fading is investigated. A general channel model is then established by considering frequency impact. A reciprocal channel construction framework is finally created. Numerical results demonstrate that our algorithm can construct bidirectional channel coefficients with high correlation and thus enable key generation technology to be used in FDD systems.