Cloud Computing enables the remote users to access data, services, and applications in on-demand from the shared pool of configurable computing resources, without the consideration of storage, hardware, and software management. On the other hand, it is not easy for cloud users to identify whether Cloud Service Provider's (CSP) tag along with the data security legal expectations. So, cloud users could not rely on CSP's in terms of trust. So, it is significant to build a secure and efficient data auditing framework for increasing and maintaining cloud users trust with CSP. Researchers suggested introducing Third Party Auditor (TPA) on behalf of cloud user for verifying the outsourced data integrity, which may reduce the computation overhead of cloud users. In this work, we proposed a novel integrity verification framework for securing cloud storage based on Ternary Hash Tree (THT) and Replica based Ternary Hash Tree (R-THT), which will be used by TPA to perform data auditing. Differing from existing work, the proposed framework performs Block-level, File-level and Replica-level auditing with tree block ordering, storage block ordering for verifying the data integrity and ensuring data availability in the cloud. We further extend our framework to support error localization with data correctness, dynamic updates with block update, insert, and delete operations in the cloud. The structure of THT and R-THT will reduce the computation cost and provide efficiency in data updates compared to the existing schemes. The security analysis of the proposed public auditing framework indicates the achievement of desired properties and performance has been evaluated with the detailed experiment set. The results show that the proposed secure cloud auditing framework is highly secure and efficient in storage, communication, and computation costs.

Security in cloud storage is an important aspect of cloud computing. In this paper, a novel multi-level encryption scheme which ensures security in cloud is introduced. In this scheme, a modified RSA (MRSA) key generation algorithm is used to generate the phase keys. The file is first subjected to encryption using MRSA with phase public keys. For secure transmission, a modified Vernam cipher (MVC) is applied to the file and stored in the cloud. Upon request, the file is obtained by applying inverse MVC followed by MRSA decryption using the phase private keys. This scheme was tested on different types of input files. The proposed algorithms protect the system from brute force attack. The MRSA's computational time is significantly less compared to the traditional RSA algorithm. Frequency and spectral analysis proves that MVC is strong and effective. Thus the new scheme ensures both confidentiality and integrity.