Data Integrity by Aes Algorithm ISSN

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1 Data Integrity by Aes Algorithm ISSN Alpha Vijayan Nidhiya Krishna Sreelakshmi T N Jyotsna Shukla Abstract: In the cloud computing, data is moved to a remotely located cloud server. Cloud will faithfully store the data and return back to the owner whenever necessary. It does not ensure that data stored in the server is secured and not altered by the cloud or Third Party Auditor (TPA). In order to overcome integrity the threat of integrity of data, the user must be able to use the guidance of a TPA. The TPA has experience in checking integrity of the data, which he cloud users lack, which is difficult for the owner to check.in the cloud the file should be correct, c accessible, consistent and high quality. The aim of this research is to ensuring the integrity of the data and provides the proof that data is in secured manner. Providing Cryptographic key to secure the data in the cloud. Keywords: AES, INTEGRITY, TPA, SLA.

2 1. Introduction: Cloud storage is visualized pools where data and applications are stored which are hosted by the third party. Those Companies, who desire to store their data in the cloud, buy or less storage capacity from them and use it for their storage needs. Some of the cloud storage benefits are reduce costs, provide more flexibility, reduce IT management of hardware and data, reduce management of web applications through automated updates, and provide greater storage capacity. In spite of these benefits, cloud lack in some of the Issues like data integrity, data loss, unauthorized access, privacy etc. Data Integrity is very important among the other cloud storage issues. After moving the data to the cloud, client hopes that his data and applications are secured. But that hope may fail some times that is the owner s data may be altered or deleted. In that case, it is important to verify if one s data has been tampered with or deleted. To check data, a user must download the data. If the data is very large, in which downloading to determine the data integrity may become prohibitive in terms of increased cost of the bandwidth and the time, if frequent data checks are necessary. In this paper, owner need not download the data or files to check the integrity and it provides the proofs that data is stored at a remote storage in the cloud is not modified by anyone and thereby of the data is assured. Some of the best examples for cloud storage are Amazon S3, Windows Azure Storage, EMC Atoms, Files Anywhere, Google Cloud Storage, Google App Engine Blob store, Cloud by Apple. 2. Cloud Storage: The process of storing data in the remotely located cloud servers are said to be cloud storage. The Architecture of cloud storage shown in fig. 1.Cloud storage is better than all storage method. Because of the following reasons. i. There the companies need not install the physical devices in their own offices. ii. The companies want to pay only for the storage they use. iii. The backup and the purchasing additional storage are offloaded to the service provider. International Journal of Innovative Research and Studies Page 121

3 Figure 1 3. AES Algorithm: It is symmetric key algorithm. In which the sender and the receiver use the same key for the encryption and decryption. Here the data block length is 128 bit and the length can be 128,192,256 bits. This is an iteration algorithm and each iteration is called Rounds and total number of rounds for 128,192,256 is 10,12,14 respectively.128 data block is divided into 16 byte and it is mapped to 4x4 array called states. The four iteration rounds are Sub Bytes, Shift Rows, Mix Columns, and Add Round Key. During Sub Bytes, a lookup table is used to determine what type replaces each byte. The Shift Row step has a certain number of rows where each row of the state is shifted cyclically by a particular offset, while leaving the first row remain as it is. Each byte of the second row is shifted left, by an offset of one, each byte in the third row by an offset of two, and the fourth row by the offset of three. Shifting is applied to all the key lengths, though there is a variation for the 256-bit block,here the first row is unchanged, the second row is done by one, the third by three, and the fourth by four. The Mix Columns step is a mixing operation using an invertible linear transformation in order to combine the four bytes in each column. The four bytes considered as input which is generated as output. The AES algorithm takes the input 4 word that is, 16 bytes and produce a linear array of 44 words that is, 176 bytes. This provide a 4 word round key for the initial round key stage and each of the 10 round of the cipher (fig 2). International Journal of Innovative Research and Studies Page 122

4 Figure: 2 Key Expansions 4. Literature Review: Cloud is the collection of computers that are connected to a common network that are internet. The user can store his own file in cloud storage that reduces maintenance cost of individual system. This paper is mainly focus on how to provide efficient integrity. Integrity means checking the correctness of the data that stored on the server[1].the user can store the data in the server is based on an agreement called SLA(Service Level Agreement)[1].To increase the computation power and to reduce the bandwidth consumption we need not encrypt the entire data. For this purpose we are dividing the file into certain size of blocks and select random bits from the block. Then encrypting these bits based on the AES algorithm. These encrypted data is called meta data and this is attached with the file and save in the server side. The key that used for decryption is same that used for encryption. Third party can change the data that save in the server side and when the client verifies that, he may came to understand that the integrity is lost [2]. Jules and Kaliski [3] proposed a scheme called Proof of Retrivability, which means that verify the data stored by the user in the cloud. This will check whether the cloud is modified the data or not. Here the cloud needs to access only the small portion of the file instead of accessing the entire portion. The huge size file is named as sentinels. Sravan and saxena [4] proposed a Systematic view of a proof of retrievability based on inserting random sentinels in the data file. Our secession discuss about various aspects to achieve data integrity. If a company wishes to move for cloud storage then there must be an authorized user and register themselves as client. A secret key is for every authorized user and this key is used for International Journal of Innovative Research and Studies Page 123

5 the login. In our paper the unauthorized user are not permitted to use the secret key and not permitted to login. At the time of file upload, the key is generated and sends this to the owner. For every uploaded file TPA verifies that the data is ecured or not. The verification can do in 2 ways Direct Verification and Download Verification. 5. Conclusion: In cloud computing the user store data in the cloud.it reduces maintenance cost and storage capacity of individual computers. The user can store data in the cloud only by an agreement called SLA. Our system provide the data integrity and the client can check the integrity of the data stored in the server. If any modification is did by the third party then it will immediately inform to the user. Thus we can provide the secure data integrity and security. AES encryption is an efficient for both hardware and software. Hardware implementation is more secured and it is mainly used for wireless security. International Journal of Innovative Research and Studies Page 124

6 References: 1. Neha T and P S Murthy on A Novel approach to data integrity proofs in cloud storage Department of CSE, CMRIT, Hyderabad Department of CSE, CMRIT, Hyderabad, Oct Soumiya Rasheed on simulation of encryption using AES algorithm Department of Electronics And Communication Karunya University Coimbatore. 3. A. Juels and Kaliski., The Retrievability proofs in cloud for large files, CCS 07Proceedings. Computer and communications security Oct Sravan Kumar and Saxena, Data integrity Proofs in cloud storage in IEEE International Journal of Innovative Research and Studies Page 125