# Secure and Efficient Deduplication for Cloud Storage with Dynamic Ownership Management
## 6 Discussion
### Analytical Synthesis  
The proposed secure deduplication protocol is constructed based on Ail et al. 's SeDaSC protocol [5], aimed at improving client computational efficiency while incorporating the principles of Hur et al. 's dynamic ownership update [6]. Our proposed protocol shares similarities with the SeDaSC protocol but introduces the following key differences:  
* Mitigation of CS dependency: The CS, which encrypts data on behalf of clients, allows clients to significantly reduce their computational workload. However, due to the CS's capability to access data in plaintext, it must be completely trusted. Our proposal employs blind encryption on plaintext to prevent unauthorized access to plaintext by the CS. As a result, our protocol offers a secure solution, particularly in environments where trust in CS security is low. * Dynamic ownership update: When applying data deduplication in cloud storage environments, situations arise where ownership information changes. Two common scenarios involve either the original data owner modifying or deleting their data, resulting in the revocation of ownership, or a new client uploading data that match existing data, granting them ownership rights. Such ownership changes can occur frequently in cloud storage services and must be appropriately managed to ensure the security of the service. To solve this issue, our protocol involves the cloud storage storing data in an encrypted format using a secret key. When a change in ownership occurs, the data are re-encrypted with a new key. This newly generated key is then distributed to clients by the CS. This approach enables the prevention of revoked clients from accessing data and ensures that newly added clients cannot access previously uploaded data. * Client computational efficiency: SeDaSC optimizes client computational efficiency by assigning encryption operations to the CS. However, to generate the same ciphertext for identical data, sending plaintext to the CS is necessary, demanding trust in the CS. To address this, we implemented blind encryption on plaintext, preventing CS access to plaintext. In our proposal, blind encryption requires one hash function and one XOR operation. Table 3 highlights our protocol's superior computational efficiency on the client side. While our proposal involves more computations than SeDaSC, it still demonstrates greater efficiency than previously proposed server-side deduplication protocols. This paper introduces a protocol that extends upon the SeDaSC protocol, emphasizing enhanced safety measures and diverse security aspects. Specifically, our protocol mitigates data privacy concerns by minimizing dependency on the CS, enhances storage efficiency through data deduplication techniques, and incorporates dynamic ownership management functionality. Since our protocol is based on SeDaSC, the primary point of comparison is the SeDaSC protocol. Therefore, Table 4 provides a comparison between the SeDaSC protocol and ours concerning computational and communication overhead. In this paper, the variable \(\lambda\) denotes the size of the data. Specifically, in Table 4, \(\lambda_{P}\) denotes the size of plaintext, \(\lambda_{K}\) represents the size of the secret key, and \(\lambda_{C}\) signifies the size of the ciphertext. These variables were utilized for the analysis of communication overhead as presented in Table 4. Firstly, our protocol marginally increases the client's computational load while reducing dependency on the CS. However, it is noteworthy that the overall communication overhead remains unchanged. Secondly, for dynamic ownership management, interaction among the client, CS, and cloud is necessary. The ownership update mentioned in Table 4 occurs when the ownership group of data changes due to another client. The majority of this interaction involves XOR operations, which minimizes the burden on each entity due to the XOR operations' computational efficiency.