With the development of information and communication technologies, vehicle ad hoc networks (VANETs) have become an important primitive for innovation and transformation in the automotive industry. However, information security issues have also become increasingly frequent and severe. Key management is among the most fundamental requirements for secure communications. In the past decades, great efforts have been devoted to provide secure and effective key management solutions for VANETs. However, traditional solutions can no longer meet the evolving demands, i.e. public key encryption schemes have revealed a conflict between security and usability over long-term use. On one hand, if private keys are not updated regularly, they may be compromised or leaked, causing security issues. On the other hand, frequent key updates can lead to complex certificate management issues. To harmonize these two conflicting requirements, we propose a novel key management scheme for VANETs with an updatable private key feature. In the proposed scheme, the private key is divided into three components: one for updating historical private keys, another for introducing new private keys, and a third for linking the historical and current private keys. This design allows the public key to remain unchanged throughout the private key update process, thereby eliminating the need for certificate management. Clearly, this construction offers significant advantages over existing key management schemes and is particularly well-suited for VANETs operating in large-scale, dynamically changing topologies.