To protect network information security and prevent identity information tampering during communication, intelligent transportation systems heavily rely on cryptographic technologies to ensure data integrity, reliability, and confidentiality. Traditional Public Key Infrastructure (PKI)-based identity authentication methods suffer from issues such as long authentication latency and high resource consumption. These traditional techniques struggle to guarantee both efficiency and reliability in high-speed vehicular scenarios on expressways. This paper proposes an innovative solution that performs strong identity authentication at expressway entrances, generates lightweight network trust credentials, and pre-distributes these credentials to subsequent roadside units by leveraging the linear and enclosed characteristics of expressways. Research demonstrates that the algorithms in this method fully consider the characteristics and limited computational power of roadside embedded hardware, reducing computational delay. The authentication time can be decreased from hundreds of milliseconds with traditional PKI to the millisecond level, achieving an efficiency improvement of over 90%, while also reducing network communication overhead by approximately 80%. By integrating domestic and international research findings, this paper provides a systematic exposition from theoretical foundations, current technological status, and problem analysis to the proposed solution, offering a complete technical pathway for secure authentication in smart expressway systems.