Cloud computing requires the security upgrade in data transmission approaches. In general, key-based encryption/decryption (symmetric and asymmetric) mechanisms ensure the secure data transfer between the devices. The symmetric key mechanisms (pseudorandom function) provide minimum protection level compared to asymmetric key (RSA, AES, and ECC) schemes. The presence of expired content and the irrelevant resources cause unauthorized data access adversely. This paper investigates how the integrity and secure data transfer are improved based on the Elliptic Curve based Schnorr scheme. This paper proposes a virtual machine based cloud model with Hybrid Cloud Security Algorithm (HCSA) to remove the expired content. The HCSA-based auditing improves the malicious activity prediction during the data transfer. The duplication in the cloud server degrades the performance of EC-Schnorr based encryption schemes. This paper utilizes the blooming filter concept to avoid the cloud server duplication. The combination of EC-Schnorr and blooming filter efficiently improves the security performance. The comparative analysis between proposed HCSA and the existing Distributed Hash Table (DHT) regarding execution time, computational overhead, and auditing time with auditing requests and servers confirms the effectiveness of HCSA in the cloud security model creation.

Data outsourcing over the cloud considers the storage space minimization as an important factor for the last decade. Various existing systems such as a single key for virtual machine (VM), third-party auditing (TPA) schemes are discussed for the less storage assurance. But they suffer from the several limitations such as less security, complexity, and unaware of malicious behavior. To overcome the aforementioned issues, the dynamic key sharing model (DKSM) is proposed to preserve the privacy in the distributed cloud computing environment. A novel third-party auditor (TPA) in DKSM model monitors the service provisioning scheme in the cloud. Initially, TPA checks their privileges and allows the users to acquire the set of available VMs address with the keys. Then, we create a hash-based message authentication code for entire services prior to file splitting during the auditing process. The corresponding key after each encryption will be discarded. Henceforth, the creation of dynamic key assures the service integrity and encryption of each part. This model improves the security and privacy of the shared content in the cloud environment. On the basis of TPA verification, the user holds the encrypted key to access the file and store it in the distributed hash table. The experimental results exhibit better encryption time, decryption time, average auditing time, storage overhead, and computation overhead than the traditional method of single key-based encryption for VM in terms of document size, the number of requests, and the number of servers. The proposed DKSM evaluated privacy performance against the number of users, and the maximum performance is achieved.