The insurance industry’s multi-stakeholder structure and conflicting incentives create substantial fraud risks, particularly collusion between insurers and reinsurers, which has been overlooked in prior research. To address this gap, we propose a verifiable data sharing framework for zero-trust environments that integrates blockchain, attribute-based encryption, and digital signatures to ensure data integrity, privacy, and accountability among policyholders, insurers, and reinsurers. The framework leverages a Multi-Authority Multi-Hierarchical CP-ABE scheme to support fine-grained and dynamic access control, and an Indexed Multi-Level Key Derivation Scheme (IMKDS) to streamline key management. By deploying Hyperledger Fabric, it achieves tamper-resistant data exchange and verifiable operational records. Experimental results demonstrate efficient performance that supports real-time fraud prevention in practical insurance applications. This work provides a scalable and trustworthy foundation for secure data collaboration in the insurance sector.