Toward Secure and Auditable Data Sharing: A Cross-Chain CP-ABE Framework

Amid the increasing demand for data sharing, the need for flexible, secure, and auditable access control mechanisms has garnered significant attention in the academic community. However, blockchain-based ciphertext-policy attribute-based encryption (CP-ABE) schemes still face cumbersome ciphertext re-encryption and insufficient oversight when handling dynamic attribute changes and cross-chain collaboration. To address these issues, we propose a dynamic permission attribute-encryption scheme for multi-chain collaboration. This scheme incorporates a multi-authority architecture for distributed attribute management and integrates an attribute revocation and granting mechanism that eliminates the need for ciphertext re-encryption, effectively reducing both computational and communication overhead. It leverages the InterPlanetary File System (IPFS) for off-chain data storage and constructs a cross-chain regulatory framework—comprising a Hyperledger Fabric business chain and a FISCO BCOS regulatory chain—to record changes in decryption privileges and access behaviors in an auditable manner. Security analysis shows selective indistinguishability under chosen-plaintext attack (sIND-CPA) security under the decisional q-Parallel Bilinear Diffie-Hellman Exponent Assumption (q-PBDHE). In the performance and experimental evaluations, we compared the proposed scheme with several advanced schemes. The results show that, while preserving security, the proposed scheme achieves higher encryption/decryption efficiency and lower storage overhead for ciphertexts and keys.