# A Charging and Discharging Data Privacy Protection Scheme for V2G Networks Based on Cloud-Fog-End
###### Abstract
However, this scheme has issues with certificate management and key escrow. Moreover, the above schemes protect the identity of EV users, but charging and discharging data in V2G networks may still be eavesdropped on, so the EV users' identity and charging and discharging data must be protected at the same time. Signcryption is a cryptographic primitive that combines signature and encryption to simultaneously achieve confidentiality and unforgeability in a single logical step [22]. [PERSON] et al. [23] first proposed a scheme that combines signcryption and certificateless aggregate signatures, leading to the study of a large number of certificateless aggregate signcryption (CLASC) schemes. Aiming to achieve privacy protection in vehicular sensor network communications, [PERSON] and [PERSON] [24] proposed a CLASC scheme that satisfies confidentiality, unforgeability, forward secrecy, and conditional traceability. [PERSON] et al. [25] combined the consortium blockchain with the CLASC algorithm to achieve a lightweight and secure communication of real-time power information, but the use of blockchain in it increases the computational overhead. However, more research is needed on CLASC schemes in fog computing environments. [PERSON] et al. [26] designed a CLASC scheme for VANETs, but users can learn the master key through scalar operations, posing security risks. The CLASC scheme proposed by [PERSON] et al. [27] improved the security of the fog-based vehicular crowd-sensing road condition monitoring systems. [PERSON] et al. [28] proposed a traceable road condition monitoring scheme based on cloud-fog, saving computational resources and network bandwidth. [PERSON] et al. [29] proposed a CLASC scheme for cloud-fog-based Industry 4.0, which achieves mutual identity authentication, public verifiability, data integrity, and confidentiality. However, all the above schemes are based on bilinear mappings, resulting in large computational and communication overhead. In summary, the main contributions of this paper are as follows. 1. In order to ensure the security and reliability of V2G networks during the charging and discharging data upload process for large-scale EVs, a cloud-fog-based V2G network architecture is designed, and a charging and discharging data privacy protection scheme is proposed. 2. In the proposed scheme, we employ a pseudonym mechanism to achieve anonymity and the traceability of the EV users' identities, thus attaining conditional privacy protection. We also designed a CLASC algorithm that guarantees the security of uploading charging and discharging privacy data. 3. The proposed scheme addresses certificate management and key escrow issues; employs aggregate operations to save network bandwidth; utilizes signature and encryption operations simultaneously to simplify computational steps; and avoids bilinear pairing and exponentiation and other complex operations. 4. According to the cloud-fog-based V2G network architecture, the aggregate verification is processed by the fog layer, alleviating the computational burden on the CSO, reducing transmission delays, and improving the efficiency of the V2G network. 5. The security analysis indicates that the proposed scheme not only meets the required security features, including conditional anonymity, confidentiality, and unforgeability, but can also resist common attacks such as impersonation, replay, and DDoS. The performance analysis demonstrates that the scheme exhibits high efficiency in both computation and communication, making it suitable for V2G network environments with limited resources. This paper is structured as follows: Section 2 introduces the system model, threat model, and safety objectives of this scheme. In Section 3, a CLASC scheme based on cloud-fog-end is proposed. In Section 4, the correctness and security of the proposed scheme is analyzed. In Section 5, the performance evaluation is conducted by analyzing computational and communication costs and comparing them with other related schemes.