Published Paper Details:

Cloud computing has become an essential platform for scalable data storage and remote accessibility. However, outsourcing sensitive information to cloud environments introduces serious security challenges such as unauthorized access, data tampering, lack of transparency, and dependency on cloud service providers. Traditional encryption mechanisms provide only limited protection because data owners must manually manage encryption, access control, and secure sharing operations. To address these limitations, this paper proposes a Proxy Re-Encryption based secure cloud data sharing framework integrated with blockchain technology. The proposed architecture introduces a dedicated cryptographic agent named CryptoProxy, which performs delegated re-encryption operations on behalf of the data owner without exposing plaintext information to the cloud service provider. The framework combines Delegated Public-Key Re-Encryption, blockchain-based integrity verification, SHA-256 hashing, and immutable auditing to ensure confidentiality, accountability, and tamper resistance. Smart contracts record all file operations and access events within a private blockchain network, enabling transparent and verifiable auditing. The proposed system minimizes trust dependency on the cloud provider, supports secure multi-user data sharing, and enhances end-to-end confidentiality across the complete cloud data lifecycle. Experimental analysis demonstrates that the framework provides efficient file access management, secure re-encryption, integrity preservation, and scalable cloud governance for modern distributed environments.