Abstract

Cloud computing continues to dominate modern distributed systems, enabling scalable and on-demand services. However, secure data sharing and user privacy remain critical challenges, especially in multi-tenant and geographically distributed cloud environments. This paper proposes a privacy-preserving secure data sharing framework integrating hybrid encryption (AES-GCM + ECC) with an enhanced proxy-based re-encryption mechanism for dynamic access control. Unlike traditional RSA-based approaches, the proposed system adopts lightweight elliptic curve cryptography (ECC) and forward-secure re-encryption techniques, ensuring reduced computational overhead and improved scalability. The framework supports secure delegation without exposing plaintext or private keys, aligning with Zero Trust security models. Performance evaluation demonstrates improved efficiency in terms of encryption time, throughput, and key management compared to legacy RSA-based systems. Security analysis confirms resistance against common attacks such as replay, collusion, and man-in-the-middle attacks.