Blockchain security for cloud focuses on leveraging decentralized ledger technology to enhance trust, transparency, and resilience in cloud computing environments where data integrity, confidentiality, and access control are critical. Research papers in this domain examine how blockchain can secure cloud storage, enable verifiable data auditing, and prevent issues like single points of failure, insider threats, and unauthorized access. Studies highlight the use of blockchain-based access control models, distributed identity management, and immutable logging to strengthen accountability in multi-tenant cloud infrastructures. Smart contracts are also explored for automating secure service-level agreements (SLAs), billing, and resource allocation. At the same time, researchers address challenges such as scalability, interoperability with existing cloud systems, latency, and energy overhead. Proposed solutions often combine blockchain with techniques like off-chain storage, homomorphic encryption, and federated cloud frameworks. Overall, this body of research emphasizes blockchain’s potential to provide decentralized, tamper-proof, and transparent security mechanisms for next-generation cloud computing services.