###### Abstract  
In this contribution, we investigate the performance of an untrusted relaying system when Cooperative Jammers (CJs) are available. We propose two scenarios, Untrusted Relaying-aided Multiple Cooperative-Jammers-based Simultaneous Transmission (UR-MCJST) and an Untrusted Relaying-aided Multiple Cooperative Jammers-based Time-Division Transmission (UR-MCJTD). The performances of both UR-MCJST and UR-MCJTD schemes are investigated. The source node is the primary user (PU) that has access to a transmission bandwidth. An untrusted relay is employed for improving the reliability of the PU transmission, while CJs are invoked for improving the secrecy rate of the PU transmission. The transmission strategy for the scheme proposed in this paper is split into three unique phases. The first phase is called the broadcast-and-jamming phase, while the second phase is called the relaying phase, and the final phase is called CJ's secondary phase, which is used for transmitting the secondary user message. More explicitly, CJs transmit noise for impairing the untrusted relay node's ability to decode the message during the broadcast-and-jamming phase. In compensation for their help, CJs are allocated part of the available spectrum by the PU for their transmission during the secondary transmission phase. A Stackelberg leader-follower game was considered between the PU and the CJs, while a power control game that is based on the well-known Nash equilibrium is employed by the CJs. Furthermore, an investigation into the effect of invoking simultaneous transmission and time-division-based transmission scenarios during the CJs' secondary transmission phase was carried out. Finally, we evaluated the achievable secrecy rate of the PU and the utility rate of the CJs in our proposed scheme. untrusted relay; game theory; Stackelberg; cognitive radio; power control 202313786316 May 202316 May 202326 June 202326  
To properly scale, adapt, and deliver quantum-safe security solutions for 6G connectivity,the security of ultra-dense networks is crucial. Hence, there arises the need for a bottom-up strategy using all security planes over the general communication stack. In this regard, physical-layer security (PLS) is a leading contender [5]. PLS has attracted a lot of attention because it is capable of using the channel's impairment, including noise, fading, interference, synchronization and location, to provide security against an eavesdropper without data encryption at the upper layers [1; 6; 7; 8]. More specifically, PLS takes the advantage of the random nature of noise and fading channel for minimizing the leaking of information to an eavesdropper. Explicitly employing the Cooperative/Friendly Jammer (CJ) has been known to be one of the most important PLS methods, where legitimate nodes communicate secretly with the help of an external jammer that transmits a jamming signal to perturb the eavesdropper [9; 10]. Recently, unmanned aerial vehicles have also been investigated as CJs for improving PLS [11; 12; 13]. Cooperative communications, as mentioned in the cited work [14; 15], present an appealing approach to accomplish reliable and efficient transmission. The wireless transmission's broadcast nature enables relay terminals to receive signals without incurring additional costs. Moreover, cooperative communications generally take advantage of decreased path loss, resulting in enhanced power efficiency, as emphasized in the studies [16; 17]. The introduction of 6G presents a complex dilemma. Since the majority of connecting devices are anticipated to utilize the existing spectrum, the number of networking devices is predicted to increase at an accelerated rate, raising concerns about spectrum scarcity. This issue calls into question 6G's viability as an upcoming networking paradigm. Cognitive radio networks (CRNs) are seen as the most promising solution for resolving spectrum shortages in 6G networks [18; 19].