In recent years Cloud computing has become the infrastructure which small and medium-sized businesses are increasingly adopting for their IT and computational needs. It provides a platform for high performance and throughput oriented computing, and massive data storage. Subsequently, novel tools and technologies are needed to handle this new infrastructure. One of the biggest challenges in this evolving field is Cloud storage security, and accordingly we propose new optimized techniques based on encryption process to achieve better storage system security. This paper proposes a symmetric block algorithm (CHiS-256) to encrypt Cloud data in efficient manner. Also, this paper presents a novel partially encrypted metadata-based data storage. The (CHiS-256) cipher is implemented as part of the Cloud data storage service to offer a secure, high-performance and throughput Cloud storage system. The results of our proposed algorithm are promising and show the methods to be advantageous in Cloud massive data storage and access applications.