# A Charging and Discharging Data Privacy Protection Scheme for V2G Networks Based on Cloud-Fog-End
###### Abstract  
Due to the openness of the vehicle-to-grid (V2G) network, the upload of charging and discharging data faces severe security challenges such as eavesdropping, tampering, and forgery. These challenges can lead to privacy breaches, transmission delays, and service quality degradation. To address these issues, a V2G network architecture based on cloud-fog-end is designed, and a charging and discharging data privacy protection scheme is proposed. We employ a pseudonym mechanism to achieve the conditional privacy protection of electric vehicle (EV) users. We design a certificateless aggregate signcryption (CLASC) algorithm to guarantee the security of uploading the charging and discharging privacy data. The algorithm solves certificate management and key escrow issues, utilizes aggregate signature operations to save network bandwidth, and avoids complex computations like bilinear pairings and exponents. Additionally, the scheme delegates the aggregate verification process to the fog layer, thereby alleviating the computational burden on the cloud layer, decreasing transmission delays, and enhancing the efficiency and reliability of the V2G network. The analysis results indicate that the scheme not only meets the required security objectives, but also has lower computational and communication overheads, making it suitable for scenarios involving the charging and discharging of large-scale EVs in V2G networks. V2G network; cloud-fog-end; electric vehicle; privacy protection; pseudonyms; certificateless aggregate signcryption +
Footnote †: journal: Applied Sciences  
breathes. If the EV user identity information is leaked, it could be used for commercial promotion by some companies or even for fraudulent activities by criminals, harming the interests of the users. Furthermore, if charging and discharging data are leaked, this could lead to the issuance of incorrect control commands by the CSO, severely impacting the normal operation of the V2G network. In addition, with the rapid growth of EVs and CPs, the communication overhead between CPs and the CSO will become very large, leading to heavy computational pressure on the CSO, transmission delays, decreased service quality, and increased privacy breach risks in V2G networks. Cloud-based solutions have been proposed for this purpose [8], accompanied by additional challenges such as higher network bandwidth and latency owing to the distance between the EV and the cloud server. Fog computing [9] is considered an extension of cloud computing, shifting the storage, computation, and other functions of cloud computing from the center of the network to the edge. Fog nodes (FNs) can use batch validation to relieve computation and storage stress in the control center, as well as reduce data transmission distances, data transmission delays, and the cost of sending data [10]. To enable reliable, secure, and efficient services for the smart grids, fog computing can provide distributed computing services to users, supporting low-latency and location-aware services [11]. Therefore, fog computing architecture can also be used in V2G networks, leveraging the computing and storage resources of FNs to improve the efficiency and reliability of V2G networks [12]. In order to address the privacy protection issues of charging and discharging data in V2G networks, data-based privacy protection schemes were proposed in [13; 14; 15], mainly encrypting the data to make them difficult for attackers to obtain. However, these schemes involve complex operations and high computational overhead, which are not suitable for V2G network environments with limited resources. Identity-based privacy protection schemes were proposed in [16; 17; 18; 19] that mainly protect the users' privacy by blurring the true identity of EV users. In [20], fog computing was combined with blockchain technology to achieve the security of the EV charging process. [PERSON] et al. [21] proposed a charging identity authentication scheme based on fog computing that uses group signatures to protect the privacy of EV users.