Blockchain technology has seen rapid development since the emergence of Bitcoin, yet the issue of data silos increasingly limits its scalability and interoperability. Cross-chain solutions aim to address this challenge, but verifying identities and establishing trust across multiple blockchains remains difficult. To address the challenges posed by data silos and the complexities involved in authenticating diverse identities across blockchains, this paper presents a novel identity authentication scheme, Certificateless Cross-Blockchain Authentication (CLCBA), which introduces a dedicated identity blockchain for managing cross-chain identities, replacing conventional relay chain mechanisms. By integrating an enhanced certificateless signcryption algorithm, CLCBA enables decentralized identity registration and efficient cross-chain authentication without relying on PKI systems. We provide formal security proofs and comprehensively analyze our scheme’s resistance against three prevalent types of attacks. Experimental results indicate that our scheme demonstrates performance improvements compared with two baseline schemes, achieving time savings ranging from 16.7% to 66.2% in message generation and a 45.2% reduction in authentication time. These improvements highlight the practical potential of CLCBA in real-world consortium blockchain scenarios, such as cross-chain financial settlement, digital supply chain tracking, and multi-party enterprise identity collaboration.