Ensuring Data Storage Security in Cloud Computing using Sobol Sequence P. Syam Kumar, R. Subramanian and D. Thamizh Selvam Department of Computer Science, School of Engineering and Technology, Pondicherry University, Puducherry. India shyam.553@gmail.com, rsmanian.csc@pondiuni.edu.in and dthamizhselvam@gmail.com Abstract— Cloud computing is the next stage in evolution of the internet, which provides large amount of computing and storage to customers provisioned as a service over the internet. However, cloud computing facing so many security challenges due to the possible compromise or byzantine failures. In this paper, we focus on Ensuring data storage security in cloud computing, which is an important aspect of Quality of Service (QoS). We propose an effective and flexible distribution verification protocol to address data storage security in cloud computing. In this protocol, we rely on erasure code for the availability, reliability of data and utilize token pre- computation using Sobol Sequence to verify the integrity of erasure coded data rather than Pseudorandom Data in existing system. Unlike prior works, our scheme provides more security to user data stored in cloud computing. The performance analysis shows that our scheme is more secure than existing system against Byzantine failure, unauthorized data modification attacks, and even cloud server colluding attacks. Keyword: Cloud computing; Data storage security; Availability; Reliability; Integrity; Pseudorandom data; Sobol sequence I. INTRODUCTION Cloud computing is an internet based computing. It dynamically delivers everything as a service over the internet based on user demand, such as network, operating system, storage, hardware, software, and resources. These services are classified into three types: Infrastructure as a Service (IaaS), Platform as a Service (PaaS) and Software as a Service (SaaS). Cloud computing is deployed as three models such as Public, Private, and Hybrid clouds [1]. Cloud data storage (Storage as a Service) is an important service of cloud computing referred as Infrastructure as a Service (IaaS). Data storage in cloud offers so many benefits to users: 1) It provides unlimited data storage space for storing user’s data. 2) Users can access the data from the cloud provider via internet anywhere in the world not on a single machine. 3) We do not buy any storage device for storing our data and have no responsibility for local machines to maintain data. Amazon’s Elastic Compute Cloud (EC 2 ) and Amazon Simple Storage Service (S3) ([2], [12]) are well known examples of cloud data storage. On the other side along with these benefits’ cloud computing faces big challenge i.e. data storage security problem, which is an important aspect of Quality of Service (QoS). Once user puts data on the cloud rather than locally, he has no control over it i.e. unauthorized users could modify user’s data or destroy it and even cloud server collude attacks. Cloud users are mostly worried about the security and reliability of their data in the cloud. Amazon’s S3 [3] is such a good example. The following research works have been highlighted the importance of ensuring integrity and availability of outsourced data. POR schemes ([4]-[6]) efficiently verifies the server for outsourced data storage correctness. G.Atenies et al. [7] introduced a Provable Data Possession (PDP) scheme; it efficiently detects the large no of file corruptions. In addition to the PDP scheme, R.D.Pietro et al. [8] introduced a Scalable Data Possession (SDP) to verify the integrity of remotely stored data dynamically. However, all the schemes could’t addresses all security threats in cloud data storage, since they work only for single server. In the complementary approach, researchers also proposed a distributed protocols ([9]-[11]) to verify the data storage security on multiple servers, but these schemes will not addresses all security issues of cloud data storage. Recently, Wang et al. [12] proposed a homomorpic distributed verification protocol to ensure data storage security in cloud computing using Pseudorandom Data. Their scheme achieves the storage correctness as well as identifies misbehaving servers. However, this scheme was not providing full protection for user storage data in cloud computing, because Pseudorandom Data does not cover the entire data while verifying the cloud servers for data storage correctness i.e. some data corruptions may be missing. In this paper, we propose a distributed verification protocol to guaranty the data storage security in cloud computing. This scheme uses Reed-Solomon erasure code [13] for the availability and reliability of data and utilizes the token pre-computation using Sobol Sequence[14] rather than Pseudorandom Data [12] to check the integrity of erasure coded data in cloud data storage. Our method achieves the integrity of storage correctness guaranty and identification of misbehaving servers i.e. whenever data modifications or deletions have been detected during the storage correctness verification across cloud servers, this method should guarantee the identification of misbehaving servers. Compared to previous methods, our method should provide more security to users data stored in cloud computing. Figure 1 shows the comparison of Pseudorandom Data and Sobol Sequence. 217 Proceedings of the 1st International Conference on Parallel, Distributed and Grid Computing (PDGC-2010) 2010 1st International Conference on Parallel, Distributed and Grid Computing (PDGC - 2010) 978-1-4244-7674-9/10/$26.00 ©2010 IEEE