With the widespread application of Internet of Vehicles (IoV) technology in smart city construction, its advantages in traffic management, intelligent driving, and information sharing have been fully demonstrated. Through communication and data interaction between on-board devices, the IoV enables more efficient traffic flow management and safer driving experiences, significantly improving the intelligence level of transportation systems. However, this widespread application also results in severe security and privacy challenges. In the open IoV environment, while increased transparency and frequent data interactions enhance system intelligence and transparency, they also increase the risk of data leakage and identity forgery. The IoV system now faces a variety of security threats, including Man-in-the-Middle Attacks (MIMMS) and replay attacks. To address these challenges, secure data authentication without compromising privacy protection and system efficiency is crucial in the evolution of IoV technology.In response to identify forgery and data tampering during data interaction, this paper proposes an identity-based proxy homomorphic signature scheme. This scheme allows users to delegate signing authority to agents through a proxy signature mechanism, ensuring the legitimacy of signatures and nonrepudiation of data, thus providing reliable security for data transactions and information sharing. A timestamp mechanism is introduced, embedding a timestamp into the signing process to ensure the timeliness of proxy signatures, effectively preventing their expiration or abuse, thereby enhancing security and credibility. The scheme’s correctness and security are strictly proven. In terms of correctness, legal proxy signatures can be correctly generated. In terms of security, the scheme’s resistance to selected message and identity attacks is analyzed and demonstrated.