The popularity of cloud technology is expanding day-by-day not only to the enterprises but also to the smart phone users due to its various service models available at lower cost. The storage service is one of the widely used service to outsource massive amount of data. With the growth of internet facility and availability, the massive amount of data is being outsourced to cloud storage server with duplicate entries. The duplicate data at server may leads to the consumption of more computational resources.It is essential to prevent the redundant data at cloud storage server to improve efficiency of storage service. These outsourced data contains sensitive information like health related information and can be compromised by inner and outer adversaries. Therefore, safety and security of sensitive information is essential in the cloud computing, but conventional crytosystem and deduplication contradicts to each other due to private keys used for encoding and decoding process, and also current cryptosystems are suffers from content distribution attack, fake key and fake ownership claiming attacks during data deduplication process. Therefore, This paper presents Finite State Automata based one-key cryptosystem and Hash-based indexing technique to achieve secure data deduplication process. The statistical analysis is carried out on system and results shows the strength of the proposed algorithms. The paper also presents Proof of Ownership and Data Integrity Verification protocol to protect the data from unauthorized access and modification. The overall analysis and results shows the strength of proposed approach as compared to existing system in reducing the utilization of computational resources.