<p>The state-of-the-art review comprehensively examines access control mechanisms for securing cloud computing environments, emphasizing their architectural evolution and performance efficiency. Conventional access control models such as Role Based Access Control (RBAC) and Attribute Based Encryption (ABE), though widely adopted, continue to face limitations including single points of failure, centralized policy management, and limited transparency in audit trails. Recent studies report average encryption and decryption times below one second in conventional schemes, yet these models struggle with scalability and dynamic revocation in distributed settings. The integration of blockchain technology addresses many of these challenges through its decentralized, immutable, and transparent infrastructure. Blockchain based access control frameworks implemented on platforms such as Hyperledger Fabric and Ethereum leverage smart contracts to automate policy enforcement and achieve throughput gains of up to 42 percent with transaction latencies near 39 milliseconds. By distributing trust and enabling verifiable audit trails, these models enhance data integrity, accountability, and compliance. This survey consolidates and analyzes current research in both conventional and blockchain based access control for cloud and IoT ecosystems, identifying performance tradeoffs, regulatory considerations, and future research directions toward secure, transparent, and scalable access management.</p>