# Secure and Efficient Deduplication for Cloud Storage with Dynamic Ownership Management
## 1 Introduction  
In the era of the fourth industrial revolution, digital technology permeates every aspect of our lives, generating vast amounts of client data in real time. The collected data are used in extensive big data analyses, applied in diverse areas including pattern recognition and predictive analytics. Companies leverage client data to formulate effective business strategies, while individuals enjoy personalized services tailored precisely to their needs. Social media: Social media platforms generate a wide range of data daily, including posts, photos, and videos. And, they captures client activities and interests for the purpose of delivering personalized content and targeted advertising. Search the Internet: Search engines such as Google (90.82%), Yahoo (3.17%), and Bing (2.83%) analyze clients' search terms and click behavior to improve search results, providing personalized information and advertisements [1]. Internet of Things: Internet of Things (IoT) devices gather diverse environmental data such as temperature, humidity, and location in smart cities and homes. The collected data are used to improve the client convenience and energy efficiency. As a large volume of data is rapidly generated and accumulated, discussions have arisen about efficient methods to manage these data, and one of them is cloud services. Cloud services provide a virtual server environment that grants clients access to intangible IT resources, including software and storage, with costs incurred only for actual usage. This not only reduces expenses linked to local equipment management but also mitigates the risk of data loss. Furthermore, cloud services offer the convenience of seamless data access,enabling clients to manage and retrieve their data from anywhere with an Internet connection. The advent of cloud services has effectively transcended the physical limitations of local computing power and storage. Deduplication technology is widely employed in cloud storage to minimize service space and lower bandwidth requirements. Deduplication refers to not storing uploaded data twice if they already exist in cloud storage. Instead, the information of the client who uploads the data is linked to the identical data in the cloud storage. Clients who own the same data can access and retrieve them within storage [2]. Data deduplication has the potential to save up to 90% of storage space while providing the same advantages as storing data multiple times [3]. It is important for clients to take into account various security concerns while utilizing the service. Individual clients may express concerns about potential leaks of personal information, while corporate clients may worry about service interruptions or the disclosure of confidential data. To address these security concerns, clients should have the option to directly encrypt and upload their data. However, when clients encrypt and upload data, there is a high likelihood that they might use different secret keys. Encrypting the same data with different secret keys will result in different ciphertexts. When cloud storage attempts to check for data duplicates, it becomes difficult to confirm if different ciphertexts are derived from the same plaintext. Consequently, data deduplication becomes unfeasible. A solution to this problem is the introduction of a new encryption approach for data deduplication, called convergent encryption (CE) [4]. In CE, encryption keys are derived directly from the data themselves. More specifically, the hash value of the data is used as the encryption key, which generates the same encryption key (and thereby the same ciphertext) from the same data. Consequently, it becomes feasible to deduplicate encrypted data for multiple clients sharing the same data. There are various ways to use cloud storage securely. If the clients uploads the data directly, then the client should encrypt their own data during upload and go through extra steps by themselves.