Integrated Communications and Security: RIS-Assisted Simultaneous Transmission and Generation of Secret Keys

TL;DR

The paper addresses secure integrated communications by leveraging a RIS to jointly optimize data transmission and physical layer key generation under a smart attacker. It develops a secure transmission ST game, proves Nash equilibrium existence, and derives a static NE, while introducing a deep recurrent Q-network DRQN-based dynamic strategy to learn RIS phase configurations under partial attacker CSI. The results show that the DRQN approach approaches exhaustive-search performance and enables one time pad communication by appropriately weighting data and key generation, highlighting a practical, endogenous security paradigm for ICAS. This work demonstrates the potential of RIS-enabled ICAS to enhance both reliability and secrecy in time-varying wireless environments, with detailed complexity analyses and simulation validation.

Abstract

We develop a new integrated communications and security (ICAS) design paradigm by leveraging the concept of reconfigurable intelligent surfaces (RISs). In particular, we propose RIS-assisted simultaneous transmission and secret key generation by sharing the RIS for these two tasks. Specifically, the legitimate transceivers intend to jointly optimize the data transmission rate and the key generation rate by configuring the phase-shift of the RIS in the presence of a smart attacker. We first derive the key generation rate of the RIS-assisted physical layer key generation (PLKG). Then, to obtain the optimal RIS configuration, we formulate the problem as a secure transmission (ST) game and prove the existence of the Nash equilibrium (NE), and then derive the NE point of the static game. For the dynamic ST game, we model the problem as a finite Markov decision process and propose a model-free reinforcement learning approach to obtain the NE point. Particularly, considering that the legitimate transceivers cannot obtain the channel state information (CSI) of the attacker in real-world conditions, we develop a deep recurrent Q-network (DRQN) based dynamic ST strategy to learn the optimal RIS configuration. The details of the algorithm are provided, and then, the system complexity is analyzed. Our simulation results show that the proposed DRQN based dynamic ST strategy has a better performance than the benchmarks even with a partial observation information, and achieves "one time pad" communication by allocating a suitable weight factor for data transmission and PLKG.

Figures (11)

• Figure 1: The schematic diagram of the three component RIS-assisted simultaneous transmission and generation of secret key in the presence of a smart attacker.
• Figure 2: The schematic diagram of the simultaneously transmitting and generating secret key at the receiver side. The secret key is generated from CSI estimation via pilot and stored in the key pool. The receive data is decrypted by the secret key of the key pool in real time via an XOR operation.
• Figure 3: Schematic diagram of the Markov decision process for RIS-assisted simultaneous transmission and generation of secret key.
• Figure 4: Illustration of the DRQN based dynamic ST strategy for the RIS-assisted ICAS system in the presence of a smart attacker.
• Figure 5: The convergence of the proposed DRQN based dynamic ST strategy for different learning rates.

Theorems & Definitions (12)

• Proposition 1
• Definition 1
• Definition 2
• Proposition 2
• Proposition 3
• Remark 1
• Remark 2
• Remark 3
• Remark 4
• Definition 3