Target active and passive eavesdropping for improving communications security

Scientists have developed an intelligent reflecting surface technique to improve the security of communication systems. The IRS-aided technique achieved more secure communication in scenarios involving both active attacks and passive eavesdropping on a two-phase communication system. The research team, with scientists in China and the United Kingdom, published its findings on April 29 in the journal Intelligent and Converged Networks at DOI: https://doi.org/10.23919/ICN.2022.0001.

In recent years, the intelligent reflecting surface (IRS) has emerged as a promising technique that enhances the function and capabilities of wireless networks. An IRS, also known as a reconfigurable intelligent surface (RIS), is a programmable structure consisting of large amounts of passive and low-cost reflecting elements. The research team has shown that the IRS can change the reflection direction of a signal, allowing it to enhance the received signals coming from legitimate users, while also suppressing the signals coming from the eavesdropper. The IRS holds the potential to lessen the interference, extend the coverage area, and improve the physical layer security communication. Its ease of use is a plus too. The IRS can be readily coated on existing buildings, for example on ceilings and walls, which reduces both the cost and complexity of installing it. “The IRS provides a cost-effective and energy-efficient approach, thus holding great promise for security enhancement,” said Gui Zhou, a lead author on the study and a Ph.D. candidate at Queen Mary University of London.

Generally, eavesdroppers work in two ways. In an active attack, the eavesdropper pretends to be a legitimate user and misleads the base station into sending signals toward it during the channel estimation procedure. By comparison, a passive attack is even more challenging to detect because the passive eavesdropper can hide itself. Previous research has shown the benefits of IRS in physical layer security under the threat of active attacks. But that earlier research often assumed perfect channel state information for the eavesdropping channels at the base station. Those conditions are both strict and impractical. Where the previous research has explored imperfect channel states, they were looking at scenarios involving active attacks. This new research is the first to examine the scenario of passive eavesdropping in IRS-aided secure communication.

In the scenario that the team studied involving a two-phase communication system, the base station avoided direct transmission to the attacked user in the first phase. Then other users cooperated in forwarding signals to the attacked user in the second phase, with the help of IRS and energy harvesting technology.

The team proposed this IRS-aided two-phase secrecy communication scheme for a scenario where the eavesdropper has a similar channel direction as a legitimate user. They chose this scheme in order to acquire high-quality eavesdropping information. In specific terms, the base station transmitted signals to the legitimate user with low transmission power during the multicasting phase to reduce information being leaked to the eavesdropper. In the user cooperation phase, other legitimate users used the energy harvested in the previous phase to forward the received signals to the attacked legitimate user with the assistance of IRS. The team studied both active attack and passive eavesdropping in this scenario.

During the eavesdropping scenario and in the presence of partial channel state information, the team investigated a beamforming design problem. In beamforming, the wireless signal is focused on a specific receiving device, instead of being broadcast in all directions, resulting in faster, more reliable connections. During both the active attack and the passive eavesdropping, with partial channel state information, the team developed a beamforming design that maximizes the security rate.

Looking ahead to future studies, the researchers say that their next step is to consider a situation where a reflection link exists between the base station and IRS, where the eavesdropper can also receive the information leaked from the IRS at the first phase. This would increase the obstacle of eavesdropping suppression. “The ultimate goal is to use IRS technology to improve physical layer security under imperfect channel state information,” said Zhou.

The research teams include Gui Zhou and Kok Keong Chai from Queen Mary University of London, United Kingdom; Cunhua Pan and Hong Ren from Southeast University, China; Kezhi Wang from Northumbria University, United Kingdom; and Kai-Kit Wong from University College of London, United Kingdom.

The paper is also available on SciOpen (https://www.sciopen.com/home) by Tsinghua University Press.

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About Intelligent and Converged Networks 

Intelligent and Converged Networks is an international specialized journal that focuses on the latest developments in communication technology. The journal is co-published by Tsinghua University Press and the International Telecommunication Union (ITU), the United Nations specialized agency for information and communication technology (ICT). Intelligent and Converged Networks draws its name from the accelerating convergence of different fields of communication technology and the growing influence of artificial intelligence and machine learning.

About SciOpen 

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