Analysis on Secure Data sharing using ELGamal s Cryptosystem in Cloud

Transcription

1 Analysis on Secure Data sharing using ELGamal s Cryptosystem in Cloud M.Jayanthi, Assistant Professor, Hod of MCA.E mail: [email protected] MahatmaGandhi University,Nalgonda, INDIA. B.Ranganatha Rao,Assistant professor, HOD of MCA,E mail: [email protected] P.G.College,secunderabad,O.U,INDIA Abstract: Cloud computing provides infrastructure less architecture. It creates a centralized data storage in one location and any authorized user involves to share the data without having required resources at their side. It has been becoming highly mandatory to the cloud storage since the growth of personal mobile devices have enhanced. The major character of the cloud is to access the data from unknown machine or resource e. Even cloud providing a large amount of data Storage and its flexibility and availability, there are many security issues of data sharing. Providing high security for the data such as economic, health information is challenging task. In this paper, ELGamal cryptosystem is used for the encryption and decryption of signing messages in order to make them authentic in cloud network. Keywords: cloud storage, ELGamal, cryptography, security. 1. Introduction: Cloud computing has a tremendous growth in technology with it minimum architecture and easier maintenance. Cloud computing is providing the rich services through the data. The cloud services are managed and maintained by the third parties called Cloud Services Providers (CSP) at remote locations. So far, the cloud offers little plat form level support or user data a protection []. In Cloud the fundamental aspect is data sharing on with other. It is very flexible, easy and less expensive on hard ware or software. Cloud allows clients to allocate resources dynamically without sophisticated deployment and management and major fundamental service of the cloud is data storage. The users of this data fully released from cumbersome task of local data storage and maintenance. Specifically data servers (cloud servers) managed by cloud server providers. But cloud providers may not fully trusted by user. Because of sensitive data storage on cloud such as business plans, cloud computing is facing security problems in cloud. So the fundamental issue is data security. It is not an easy task of secure data sharing among groups in cloud. Cloud provides service models (SaaS, PaaS and IaaS) and deployment model. Security issues in cloud categorized in two ways: 1. By cloud providers and 2. By their customers. Both

2 providers and customers must ensure each other if the data are protected. User must take measures to use strong passwords and authentication measures. Present days most of the algorithms provides security for the data sharing trough the network. In this paper, ELGamal s cryptosystem[11] [12] is presenting to prevent the data storage in cloud network. Rest of the paper explains about 2. Related work 3. Security issues 4. Cryptosystem 5. ELGamal s cryptosystem 6. Conclusion 7. References. 2. Related work: With growth of cloud computing increases frequent cloud security incidents. The main issues are well established challenges such as phishing [7], downtime [8], data loss [9], and password weakness [10]. To date, most papers published on cloud security reflect continuations of established lines of security research such as web security, data out sourcing and assurance and virtual machine. In cloud storages, researchers have conveyed two fundamental approaches to check the availability and integrity that are PDP [13] and POR [14]. Some of them use RSA-based scheme. They also proposed a publicly verifiable version, which allows any one, not just owner, to challenge the server for data owners and users. However, these schemes are not secure completely against replay attacks. In cloud, to achieve secured data sharing among number of researchers used different schemes. The process of encryption and decryption is known as cryptography. This cryptography is useful design to secure and preserve privacy and also used to provide support to verify identity and integrity of data. In [5], kallahalla et.al introduced a cryptographic storage system. By dividing files into file groups and each file group is encrypted with a unique file block key. Lu et. Al [6] proposed a secured group signature and cipher text policy attribute-based encryption technique. In this paper, ELGamal s encryption is used to obscure the contents of a message so that it cannot be read by unintended recipient. 3. Security issues and privacy: Cloud computing security is a sub domain of computer security. It means a broad set of schemes, technologies and controls deployed to protect data, applications and infrastructure of cloud computing. There are different types of controls in a cloud security such as deferent controls and preventive controls, detective controls, corrective controls. Issues: Security issues in cloud identified in many areas. i). identity management: Cloud providers may integrate the customers identity management system into their own infrastructure or provide an identity management solution of their own.

3 ii). Physical security: Cloud service providers should provide security for physical IT hardware such as server, routers, cables etc against unauthorized access, references theft, fires, floods, etc... iii) Availability: Cloud providers keep the data available to all users and applications. This availability of data for all the users is not secure. It may affect the personnel data from unauthorized users. iv) Privacy: In cloud storage, data privacy is a hot issue. Since data is available for all the users the private data storage is not possible. So it is crucial this to discuss about privacy of the data in cloud. Continues increments in technology is also providing the security for the data.there are multiple mechanisms to preserve the data in cloud. Cryptography is taking main role in computer technology to protect the data from malicious attacks. 4. CryptoSystem: Cryptography [2] is revolutionary method in whole technological study.it uses secret keys to disappear the actual text and vice versa. It is a simple mathematical technique. Using cryptosystems the plain text can be converted into cipher text. Cipher text is not understandable to human being. And also its not simple task to know the cryptographically performed process on data without any prior knowledge. Naturally, the cryptography can be symbolized as Decr ( Encr (data))=data It contains two methods first is encryption (Encr) and other is decryption (Decr). One of these methods can perform on every end of communicating systems. The man attribute of this process is a key. It is a secrete piece of information. i. Encryption key: encryption is the process of converting the plain text into not understandable format. The key which is useful to perform this process is known as encryption key. ii. Decryption key: reversing process of encryption i.e. retrieving the actual text is known as description. It needs a key called decryption key. Cryptography process can be express in two ways. i. Symmetric: This type needs only single key to encrypt and decrypt the message. ii. Asymmetric: In this type, the key can be split into two parts. One is public key and other is private key. Many of the researchers proposed different cryptography algorithms such as Diffiehellman public key cryptography [1], shanks, and the pollard cryptography. Taher ELGamal first described the cryptosystem [] in an article. Elgamal algorithm is also public key cryptographic algorithm. The private key will be hidden. So if the private key is not known, as we

4 know, it is not possible to reveal the message. So encryption and decryption of message will provide more security for the data. 5. Elgamal s cryptosystem: Even diffie and Hellman algorithm providing security, it needs interaction of both parties to estimate private key. But some situations any of the both parties is not able to interact in the same time. In this paper, to provide the security for the cloud storage ELGamal used simplified the method of Diffie-hellman private key. So encryption and decryption takes different directions. i. ELGamal keys generations: ELGamal s algorithm [3] [4] uses discrete logarithm so it is hard to solve. Let s suppose a sender wishes to send a message M to a receiver. The cipher text represented as a pair(y, C). Y= g a mod P C= x b M (mod P) The recipient may obtain the message by finding M. M= C / Y a (mod P) Here, P= large prime from message space Z* p g=generator from Z* p a= private key from Z p-1 ii. ELGamal signatures: ELGamal crypto system also provides the signature to the message M. this ELGamal signature will be done through the discrete logarithms so in cloud networks. The storage data will not be known by unknown person. This signature makes invalid the authorized person or resource. a) Creation of signature: Data owner has to find the signature using his/her own private key a. then he upload the data as pair of data and signature i.e. (d, s). b) User verification: The authorized user verifies the signature with his / her public key. In cloud storage system, the cloud user should perform this task. This allows the authorized users as they have public key. c) Prevention: This signature is not possible to forge by unauthorized user for an arbitrary message. iii. Procedure of signing : Signing procedure on data follows below steps. Step 1: Step 2: Select a random key k from G Calculate r = g k mod P

5 Signature in ELGamal is (r, s) where 0<=r, s<p-1. Transactions on Information theory, IT- 22(6): ,1976 Step 3: i.e. g D = (g a ) r r s mod P 3. ELGamal T. A Public Key Cryptosystem and a Signature Scheme Based on Descrete Logarithms. Information Theory. IEEE Transactions. 1985: 31(4): Step 4: Solve it for S From sept 2, it is obtained g D = g ar g ks g D = g (ar+ks) mod P D= ar+ks mod (p-1) mod P If k is assumed as obtaining GCD (k, P-1) =1, then it gives a solution for S. The cloud user receives (D, r, s) and verify this signature now. 6. Conclusion: ELGamal s cryptosystems has many useful applications, with its strong properties. It is a very securable algorithm. This is not prohibitively difficult to encrypt the message in cloud also. It is not possible to forge the signature so the authorized users can share this data more securely. 7. References: [1]. Dan Boneh, The decision Diffie-Hellman problem. Lecture notes in computer science, 1423:48-63, [2]. Whitfield Diffie and Martin E. Hellman. New Direction in Cryptograpy. IEEE 4. Tsiounis Y.Yung M. on the security of ELGamal Based Encryption. Lecture notes in computer science [5] M. Kallahalla, E. Riedel, R. Swaminathan, Q. Wang, and K. Fu, Plutus: Scalable Secure File Sharing on Untrusted Storage, Proc.USENIX Conf. File and Storage Technologies, pp , [6]. R. Lu, X. Lin, X. Liang, and X. Shen, Secure Provenance: The Essential of Bread and Butter of Data Forensics in Cloud Computing, Proc. ACM Symp. Information, Computer and Comm. Security, pp , [7] Gone phishing. Twitter Blog. January 03,2009. [8]. E.Knorr. Gmail follies and Google s enterprise pitch.infoworld. September 8, [9] J.Stokes. T-Mobile and Microsoft/Danger dara loss is bad for the cloud. Ars technical. October []0]. D.Raywood. the twitter hacking incident last week should be a call to better security awareness and not about cloud storage.sc Magazine. July20,2009. [11]. Andreas V. Meier. The ELGamal cryptosystem.june 8,2005.

6 [12].Taher ELGamal. A public key cryptosystem and a signature scheme based on discrete logarithms.in Proceeding of CRYPTO 84 on Advances in cryptology,pages 10-18, Springer-verlag New York,Inc.,1985. [13]. G. Ateniese, R. C. Burns, R. Curtmola, J. Herring, L. Kissner, Z. N. J. Peterson, and D. X. Song, Provable data possession at untrusted stores, in ACM Conference on Computer and Communications Security, P. Ning, S. D. C. di Vimercati, and P. F. Syverson, Eds. ACM, 2007, pp B.Ranganath Rao M.C.A.,M.Tech.,M.L.I.Sc., M.Com.,( Ph.d in Computer) has been working as Asst.Professor in Computer Science,Department of Computers,HOD, OU PG College, Secunderabad, Telgana State. His areas of interest are management,unix and web Mining, and object oriented system development. [14] A. Juels and B. S. K. Jr., Pors: proofs of retrievability for large files, in ACM Conference on Computer and Communications Security, P. Ning, S. D. C. di Vimercati, and P. F. Syverson, Eds. ACM, 2007, pp Biography : M.Jayanthi Assistant professor in Department of Computer Science and informatics, University college of Engineering, Mahatmagandhi University, Nalgonda. Her research interests are software engineering, cloud computing and networks.