Storage Based Time Efficient Data Retrieval in Cloud

IJIRST –International Journal for Innovative Research in Science & Technology| Volume 3 | Issue 01 | June 2016 ISSN (online): 2349-6010

Storage Based Time Efficient Data Retrieval in Cloud S Nirmalraj University College of Engineering (Bit Campus), Tiruchirappalli 620 024

Abstract To protect outsourced information in cloud storage against corruptions, adding fault tolerance along with information integrity checking and failure reparation becomes critical. Recently, regenerating codes have gained familiarity because of their lower repair information measure whereas providing fault tolerance. This paper implements Data privacy by randomizing the encode coefficients with a pseudorandom function with public auditing and proxy regeneration method which reduces data owner online burden for data integrity checking and reparation respectively. We analyzed that the existing storage scheme requires more time for retrieving repaired data. This paper proposes a naive storage based technique which replaces the merged storage of split files at different servers into individual split file storage (such as A, B, C instead of AB, BC, CA). Thus this paper provides performance analysis of reduced time complexity during retrieval of large collection of long time archival data for future usage.

Keywords: Cloud Storage, Regenerating Codes, Public Auditing, Proxy, Third Party Auditing, Data Retrieval _______________________________________________________________________________________________________ I.

INTRODUCTION

Cloud Storage is gaining popularity because of its flexible on-demand data outsourcing service with appealing benefits such as:  Relief of burden for storage management,  Universal data access with location independence, thus allowing others to access client data(with privilege) will result with collaborative working style instead of individual work,  Avoidance of capital expenditure on hardware(Storage devices), software and personal maintenance,  No need for technical experts for maintaining storage, backup, replication and importantly disaster management etc., Even though the cloud storage has lot many advantages still it emerges new security threats on user data which makes the individual or organisation feels unsecure about their outsourced data, among those the following threats should be noted with more importance, such as:  The data owner can lose his/her control over the outsourced data due to location independence, which leads to risk on the correctness, availability and integrity of their outsourced data,  The internal/external adversaries can maliciously delete/corrupt the user’s data,  The Cloud Service Providers itself may act dishonest and can attempt to hide data loss or corruption to make the data owner believe that their data are still safe and secure for their own economical beneficiaries.

Thus the Cloud users are recommended to implement their own efficient protocol for performing periodical verification of their outsourced data to ensure that the cloud service providers are still maintaining their data intactness.

From the beginning of initial cloud storage implementation, up to still now many mechanisms for dealing the integrity of outsourced data has been evolved, the most notable mechanism among those has been surveyed in this paper such as, G. Ateniese et al’s [1] Provable Data Possession at untrusted stores, Juels and kaliski’s [2] Proofs Of Retrievability for large files which are actually proposed for single server storage systems. Therefore the single server storage system are extended to be compatible for multi cloud storage system along with data integrity verification techniques from papers [3] - [9] which leads to emergence of various redundancy schemes such as Replication, Erasure codes and right now with Regenerating codes respectively.

In this paper we mainly focus on 3 aspects with respect to regenerating code based cloud storage such as Integrity verification, Data owner’s online burden during reparation (Proxy regeneration), Data Retrieval respectively. Chen et al [6] and Chen and Lee [7] performed various studies and extended the single-server CPOR scheme in [10] to the regenerating code- Scenario, [7] designed and implemented a Data Integrity Protection scheme (DIP) for Functional – Minimum storage regenerating code (FMSR) [11] - based cloud storage which maintains the same level of data redundancy and storage requirement as in traditional erasure codes, but Uses less repair traffic is adapted to the thin-cloud setting, however both [6], [7] are designed for private auditing which allows only the data owner to verify the integrity and repairing the faulty server. Though the size of the data to be outsourced by owner is considerably of large size, the resources required for auditing and repairing are necessary and expensive for the user [13]. Thus Wang’s [14] proposed to reduce the operation required in favour of user. To fully ensure the data integrity and to release data owner from online burden this paper implements a public auditing scheme for regenerating code based cloud storage in which the integrity is checked frequently by using Third Party Auditor and handles regeneration of failed

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Storage Based Time Efficient Data Retrieval in Cloud (IJIRST/ Volume 3 / Issue 01/ 040)

server with the help of Proxy on behalf of data owner as surveyed from [26]. We encrypt the data to protect the privacy of information against the auditor which is easier than [13], [14] - Proof Blind Technique and [15] – Data Blind Technique.

It is analysed that the proxy regeneration can bring new challenges and threats which can be reduced by the following steps:  A couple of secret keys can be generated as we studied in [16], which utilizes linear subspace of regenerating code that can be computed more efficiently. On behalf of data owner this scheme requires less computation devices (e.g. for authenticating data blocks).  Our scheme provides privacy against outsourced data by masking the data using pseudorandom function which avoids leakage of original data. Thus does not introduce computation overhead for cloud service provider or Third Party Auditor.  Our work completely releases the data owner’s online burden by privileging proxy for reparation.  The storage, computation, communication overheads during auditing phase can be reduced.

II. RELATED WORK The subject of remote data checking for correctness was shrewd introduced in [18] and [19]. Be suited to Ateniese et al. [1] and Juels and Kaliski [2] gave rise to the resembling notions provable Data Possession (PDP) and Proof Of Retrievability (POR), respectively. Ateniese et al. [1] proposed a formal definition of the PDP parcel out for ensuring possession of files on untrusted storage, introduced the concept of RSA-based homomorphic tags and suggested randomly sampling a few blocks of the file. In their days dissemble [20], they proposed a dynamic version of the prior PDP scheme based on Message Authentication Code (MAC), which allows very basic block operations with limited functionality but block insertions. In days of yore, Erway et al.

[21] gave a formal framework for dynamic PDP and provided the first complete dynamic solution to buttress demonstrable updates to hold on data using rank-based authenticated skit lists and RSA trees.

To improve the efficiency of dynamic PDP, Wang et al. [22] proposed a new method which uses merkle hash tree to support fully dynamic data, Worku et al. [23] proposed another efficient privacy preservation technique which avoids involving computationally expensive pairing operations for data blinding. Be suited to Browers at al. [24] proposed an improved POR protocol which continually leads to Dodis et al. [25] anatomize on various POR with private auditing. Varied storage systems pull in a tap on replication to increase the availability and durability of information on untrusted storage systems. At present, such storage systems equip no strong evidence that multiple duplicates of the information are actually stored.

Storage servers can intrigue to create it seem like they are storing several copies of the the information, while as a general rule they just store a solitary duplicate. We greet this shortcoming via multiple-replica provable data possession (MR-PDP) [3]: A provably-secure plan that permits a client that stores t copies of a file in a storage framework to confirm through a challengeresponse convention that (1) each unique replica can be made at the time of the challenge also, that (2) the storage framework utilizes t times the capacity required to store a single replica. MR-PDP extends previous enactment on data possession proofs for a single copy of a file in a client/server storage system. Applying MR-PDP to aggregate t replicas is computationally much more proficient than using a single-replica PDP scheme to store t separate, disconnected records (e.g., by scrambling all file individually before storing it). Another point of preference of MR-PDP is that it can produce additional replicas on interest, at little cost, when some of the existing replicas fail.

HAIL (High-Availability and Integrity Layer) [4], a distributed cryptographic framework that permits a set of servers to exhibit to a client that a put away record is in place and retrievable. HAIL strengthens, formally unifies, and streamlines particular methodologies from the cryptographic and distributed- frameworks groups. Proofs in HAIL are efficiently processable by servers and profoundly conservative—ordinarily tens or hundreds of bytes, regardless of file size. HAIL cryptographically confirms and responsively reallocates record shares. It is sturdy against an active, mobile adversary, i.e., one that may logically corrupt the complete set of servers. We propose a solid, formal adversarial model for HAIL, and rigorous investigation and parameter decisions. We demonstrate how HAIL moves forward on the security and efficiency of existing tools, like Proofs of Retrievability (PORs) expand on individual servers.

Remote Data Checking (RDC) [5] is a technique by which clients can build up that information outsourced at untrusted servers remains intact over time. RDC is useful as a prevention tool, permitting clients to intermittently check if information has been damaged, and as a repair tool whenever damage has been identified. At first proposed with regards to a single server, RDC was later extended to verify data integrity in distributed storage framework that depend on replication and on erasure coding to store data redundantly at multiple servers. As of late, a method was proposed to include repetition based on network coding, which offers interesting tradeoffs on account of its astoundingly low communication overhead to repair corrupt servers. Unlike previous work on RDC which concentrated on minimizing the expenses of the aversion stage, we take a holistic look and initiate the investigation of RDC plans for distributed frameworks that depend on network coding to minimize the combined costs of both the anticipation, repair stages. We propose RDC-NC, a novel secure and effective RDC plan for network coding-based distributed storage frameworks.

RDC-NC mitigates new assaults that stem from the underlying principle of network coding. The scheme is able to preserve in an antagonistic setting the denude communication overhead of the repair collaborator achieved by network coding in a benign setting. We actualize our scheme and experimentally show that it is computationally inexpensive for both clients and servers.

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Storage Based Time Efficient Data Retrieval in Cloud (IJIRST/ Volume 3 / Issue 01/ 040)

III. PROPOSED SYSTEM ARCHITECTURE System Model The System architecture for regenerating code-based cloud storage using auditing scheme consists of four entities as follows: 1) Data owner: The Data owner is the person or organization who possesses a lot of information records to be stored in the cloud. The cloud user can have permissions to access and manipulate stored data blocks. Once the data blocks are uploaded to the cloud, the TPA can view the data blocks that are uploaded in multi cloud. When the user wants to download the files, the data in multi cloud were integrated and downloaded.

2) Cloud Service Provider: The Cloud Service Provider (CSP) is the service provider that offers customers storage or software services accessible by means of a private cloud or public network, which means that the storage and software is available for access via the Internet and has significant computational resources.

Fig. 1. The System Architecture

3) Third Party Auditor: The Third Party Auditing (TPA) is a characteristic choice for the storage auditing in cloud computing.

The TPA can periodically check the integrity of the considerable number of information stored in the cloud on behalf of the users to ensure their storage correctness in the cloud which convinces both cloud service suppliers and proprietors. “TPA Based Cloud Storage Security Techniques�, minimizes the business investment and satisfy the client need in terms of web.

Client can store information and recover information from cloud when it is required. However, there is no guarantee of the information security that it is not changed by the third party auditor. Users should have the capacity to help the TPA to overcome the integrity problems in cloud. The Third Party Auditing permits to spare the time and calculation assets with reduced online burden of users.

4) Proxy Agent: The Proxy agent is a semi trusted which regenerates data blocks and failed authenticators during the repair procedure on behalf of the data owner. After uploading the data the data owner may become off-line and he/she is restricted in computational and storage assets contrasted with other entities. The proxy would always be online and it is much more powerful than that of data owner but it is less than the cloud servers in terms of computation and storage. The proxy server is delegated on behalf of reparation on behalf of data owner which saves resources as well as online burden.

For storage security the Advanced Encryption Standard (AES) used is a symmetric encryption algorithm that was designed to be proficient in both equipment and programming, and supports a segment length of 128 bits and key lengths of 128, 192, and 256 bits. It is based on a design guideline known as a substitution - permutation network, mixture of both substitution and permutation, which is efficient in both software and hardware. The key size utilized for an AES cipher indicates the number of times the repetitions of transformation rounds for change overing the information, called the plaintext, into the final output, called the cipher text.

Regenerating Codes Dimakis et al is the first who introduced Regenerating codes [17] for distributed storage for the purpose of reducing repair bandwidth. The cloud storage can be viewed as collection of n storage servers, data file that can be uploaded by user or data owner can be represented as F which is encoded and stored across redundant servers.

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Storage Based Time Efficient Data Retrieval in Cloud (IJIRST/ Volume 3 / Issue 01/ 040)

Whenever data corruption is detected, then data file F can be retrieved by communicating to any k-out of-n servers, the client can contact ℓ healthy servers and download �′ bits from each server for regenerating corrupted file without contacting the entire original file.

The Repair Bandwidth đ?›žâ€˛ = â„“đ?›˝â€˛ can be reduced with conditionâ„“ ≼ đ?‘˜. Where, đ?‘†đ?‘Ąđ?‘œđ?‘&#x;đ?‘Žđ?‘”đ?‘’ đ??śđ?‘œđ?‘ đ?‘Ą = đ?›ź and đ?‘…đ?‘’đ?‘?đ?‘Žđ?‘–đ?‘&#x; đ??ľđ?‘Žđ?‘›đ?‘‘đ?‘¤đ?‘–đ?‘‘đ?‘Ąâ„Ž = đ?›ž, the Minimum bandwidth regenerating (MBR) - least possible repair bandwidth, the minimum storage regenerating (MSR) – least possible storage cost denoted by using parameters (đ?‘›, đ?‘˜, â„“, đ?›ź, đ?›ž), which can be chosen by using the guidelines found in [6].

Based on the aspect of regeneration there are 2 versions of repair strategy has been studied in Dimakis’s [12] survey on network codes for distributed storage such as exact repair and functional repair.

Exact repair scheme requires the repaired server for storing an exact replica of the corrupted blocks, whereas Functional repair scheme generates new server for storing repaired server which may be having high probability of data variation while regenerating original information of corrupted file. Thus the functional repair strategy is more suitable for long term archival, regulatory storage, data escrow as in [6].

The functional repair strategy can reconstruct original file from any m coded blocks by solving a set of m equations. The coded blocks can be distributed across n storage servers, with every server putting away Îą blocks. Any k out of n servers can be used to recover the original data file when the inequality đ?‘˜đ?›ź ≼ đ?‘š is maintained.

When the TPA detects data corruption at one server, the repair procedure will communicate đ?‘™ servers and obtain đ?›˝ blocks from each to regenerate the repaired Îą blocks. Fig.2 shows the existing regenerative code technique for repairing failed server by communicating other survival redundant storage servers.

Fig. 2: Existing Regenerative code technique

Methodology: Our Scheme follows the procedure for setup, audit and repair as follows: Setup: When Data owner uploading data for outsourcing in cloud server,  He / She should generate key by initializing public (đ?‘?đ?‘˜ ) and secret (đ?‘ đ?‘˜ ) parameter by taking security parameter k as input to the cloud server.  The data owner delivers partial secret key x to the proxy through a secure approach.  By taking secret key (đ?‘ đ?‘˜ ) and file (F) to be uploaded as input our setup procedure outputs an Authenticator block Ф, a coded block set Ďˆ and a file tag t.

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Storage Based Time Efficient Data Retrieval in Cloud (IJIRST/ Volume 3 / Issue 01/ 040)

Audit: To check data integrity, the cloud server and TPA communicates with each other by taking random sample of blocks as input as follows,  By taking the file information (Fđ?‘–đ?‘›đ?‘“đ?‘œ ) as input, the TPA generates challenge đ?’ž to the cloud server.  The cloud server then generates proof (P) for corresponding challenge đ?’ž, authenticator set (Ф), coded block (Ďˆ) as input.  Immediately after receiving the proof generated by cloud server, the TPA verifies the data integrity by taking the proof (đ?’Ť), Public Key (đ?‘?đ?‘˜ ) and challenge đ?’ž as input.  If the verification passes the TPA outputs 1 or else 0 otherwise.

Repair: In repair procedure, the proxy interacts with cloud server in absence of data owner to regenerate the failed server detected by the audit procedure as follows,  When receiving TPA verification result, the proxy server outputs claim for repair (đ??śđ?‘&#x; ) as like challenge in audit phase.  The cloud server when receiving đ??śđ?‘&#x; with coded block (Ďˆ) and authentication block (Ф) as input, it outputs Block and Authentication set BA to the proxy server.  The proxy implements đ??śđ?‘&#x; , BA and responds new coded block set Ďˆ' and authenticator set Ф′ if successful, outputs ⊼ if not successful.

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Storage Based Time Efficient Data Retrieval in Cloud (IJIRST/ Volume 3 / Issue 01/ 040)

CLOUD SERVER

PROXY

Claim for Repair (â„ąđ?‘–đ?‘›đ?‘“đ?‘œ ) đ?’žđ?‘&#x; GenForRep(đ?’ž, Ф, đ?œ“) BA

BlockAndSigReGen(đ?’žđ?‘&#x;, BA) Ф’, Ďˆâ€™, ⊼

Fig. 3: The Sequence Charts for Setup, Audit, Repair

Proposed System Among the first few ones to support privacy-preserving public auditing in cloud computing with an attention on information storage, other than with the prevalence of cloud computing, a foreseeable increase of auditing tasks from various clients might be designated to TPA. As the individual auditing of these growing tasks can be tedious and cumbersome, a a characteristic interest is then how to empower the TPA to proficiently perform multiple auditing tasks in a bunch manner, i.e., all the while.

The public auditing system of data storage security in cloud computing using proxy and provide a privacy-preserving auditing protocol. The proxy server is allocated for repairing faulty server. It is analyzed that the time required for downloading or retrieving data from merged storage of coded blocks introduces time complexity which is shown in the performance analysis should be reduced to increase the satisfiability of cloud users. This can be implemented by modifying the storage technique for redundantly storing data with less storage requirement as shown in the Fig. 3 which clearly describes how storage can be implemented in the proposed system.

Fig. 3: Proposed storage system for reduced time complexity during data retrieval.

IV. PERFORMANCE ANALYSIS The extensive analysis shows that the outsourced data can be continuously verified for its integrity and the failed data blocks can be efficiently generated by the proxy which is then retrieved at any time with the encoding and decoding procedures simultaneously. It is analyzed and showed that our scheme is provable secure, highly efficient and can be practically incorporated into a recovering -code-based cloud storage system.

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Storage Based Time Efficient Data Retrieval in Cloud (IJIRST/ Volume 3 / Issue 01/ 040)

When uploading a file, the file can be divided into number of segments (e.g. A, B, C). And those segments are stored in more than one server (e.g. server 1, server 2, server 3) Server 1 containing A and B segments, server 2 containing B and C segments, Server 3 containing C and A segments. If anyone server fails the file in that particular server also corrupted. Then the original file will be retrieved with the help of remaining servers. It reduces the complexity to identify the file and easily recover the original file. Our modified storage technique shows that the time complexity is considerably reduced as shown in the below graph.

Fig. 4: An comparison of existing and proposed system for computation cost, Storage size and Data retrieval time.

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V. CONCLUSION Thus the public auditing scheme for regenerating code based cloud storage system delegates a TPA for data validity checking on behalf of the data owner. To protect the original data privacy against the TPA, we randomize the coefficients in the initial rather than applying the visually impaired strategy during the auditing process .Considering that the data owner cannot continuously stay online by and by, so as to keep the storage available and verifiable after a malicious corruption, we bring a semi-trusted intermediary into the system model and provide a privilege for the proxy to handle the reparation of the coded segments and authenticators. To better fitting for the regenerating-code-scenario, we design our authenticator based on the BLS signature. Also the modified storage method reduces the time required to retrieve and download the user requested file for download.

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