### Literature Review Comparison  
Most of the works consider the relaying terminal as a trusted node, while the eavesdropper is considered as an outsider that is not part of the communication infrastructure [28; 29; 30]. Furthermore, in cooperative cognitive radio networks [31], the spectrum is shared among the licensed and unlicensed users, where the relay terminals can be part of the unlicensed users. In such a scenario, the relay node may not be trustworthy and could be a potential eavesdropper [32; 33; 34]  
The concept of untrusted relays was initially explored in [35], where the destination played the role of a jammer during the broadcast phase to ensure secrecy for the source and destination pair. [PERSON] et al. [36] investigated the secrecy rate performance of an amplify-and-forward (AF) relaying network with an untrusted relay, employing destination-based jamming to enable secure transmissions. [PERSON] et al. [37] considered a two-way relaying scheme involving a large-scale multiple-antenna base station (BS), a single-antenna mobile user (MU), and a multiple-antenna external jammer, analyzing the ergodic secrecy sum rate, which was found to improve with an increasing number of untrusted relays. To enhance the secrecy rate performance of systems using an untrusted relay and a multiple-antenna destination, [PERSON] et al. [38] proposed a novel full-duplex destination jamming scheme with optimal antenna selection. The analytical curves presented in [38] were verified to align well with the simulation results. [PERSON] et al. [39] considered an untrusted relay-based network where the source transmitted a confidential message to both the relay and the destination, while the destination transmitted a jamming signal to the relay. The Non-orthogonal AF (NAF) and Orthogonal AF (OAF) protocols were examined in [39], with the source-destination (S-D) link being considered in both the source-broadcasting and relaying phases in the NAF scenario, whereas in the OAF scenario, the S-D link was only involved in the source-broadcasting phase. The topic of secrecy transmission with multiple untrusted relays was explored in [40]. Specifically, the study focused on the use of cooperative jammers to safeguard the transmitted confidential signal against eavesdropping. These cooperative jammers employed techniques such as transmitting noise [9; 41] or sending codewords [42; 43] to counteract eavesdroppers. Most of the existing works in this area have investigated jamming methods involving the destination or utilizing altruistic nodes [44; 45]. Game theoretic secrecy maximization techniques have been investigated in [34; 46; 47]. Jamming through non-altruistic nodes was considered in [48], where the communication is secured through these nodes, and in return, they are considered as the SUs in the network. Specifically, the jammers would be given access to the spectrum of the PUs for their secondary transmissions. Furthermore, a Stackelberg-based game was presented in [46], for the enhancement of the PU's secrecy rate. In the study by [PERSON] et al. in [49], a cognitive radio network (CRN) was examined, consisting of a primary transmission involving a PU transmitter (PT) and PU receiver (PR), as well as a secondary transmission involving an SU transmitter (ST) and SU receiver (SR). The ST in [49] was considered as a trusted relay for the PT, and the cooperation between the PT and ST was utilized to establish physical layer security using a multilevel Stackelberg game. Throughout the network, all transmissions were susceptible to potential eavesdropping attacks. The study demonstrated that employing spectrum leasing, where secondary access is traded for cooperation, is a promising framework for enhancing the secrecy rate in CRNs. This finding was highlighted in [49]. In [PERSON] et al. [47], a two-way untrusted relay-based network was studied, incorporating a Stackelberg game between the sources and friendly jammers.