In recent years, people are drastically using the internet. Their daily lives have grown to depend on it, and it now connects to their social lives. In addition, internet usage has increased as a result of the COVID pandemic. Data growth and the associated need for storage space have emerged as major issues in cloud storage management. To improve the efficiency of cloud storage and save bandwidth of network data transmission, the duplication of cloud data has become a research goal, especially in the field of encrypted cloud data storage. Deduplication is a technique for removing data redundancy that was created to reduce redundant data in cloud storage and conserve system storage resources. Nowadays, due to the growth of cloud computing technologies, duplication techniques are increasingly used in cloud service centers. Therefore, many researchers have adopted several deduplication methods to remove redundant data from cloud storage. For secure deduplication, previous works have typically used third-party auditors to verify data integrity, but it may be suffered from data leaks by third-party auditors. Conventional methods also could not face more difficulties in the deduplication of big data to properly consider the two conflicting goals of high deduplication ratio and deduplication efficiency. In this paper, an improved blockchainbased secure data deduplication is presented with efficient cryptographic methods to save cloud storage securely. In the proposed method, an Attribute-based Role Key Generation (ARKG) method is implemented in a hierarchical tree manner to generate a role key when the data owners upload their data to the cloud service provider (CSP) and to allow authorized users to download the data. In the storage system, the smart agreement (agreement between the data owner and CSP) is done using SHA-256 (Secure Hash Algorithm-256) to generate a tamper-proofing ledger for data integrity, in which data is protected from illegal modifications and duplication detection is executed through hash-tag that can be formed by SHA-256. Content Sealed Encryption (CSE) is employed to encrypt data for data uploading by the data owners to the CSP. The experimental results show that the proposed secure deduplication scheme is efficient according to data deduplication, storage costs, computational costs, and computation delay and it can give higher throughput and a low duplicate elimination ratio.