Now a days cloud computing plays a key role for sharing group resource among their users. Due to the frequent changes of membership maintaining multi owner data is becoming a difficult task and also sharing of data in an un trusted cloud is also a major challenge. For that purpose we introduce the MONA for dynamic groups in the cloud and it supports for group signature and broadcast encryption techniques. So that any cloud user can share data with the others. Here the revocation list is also presented. Key Words-Cloud Computing, data sharing, dynamic groups, privacy maintenance, access control. 1.INTRODUCTION Cloud computing is an internet based computing so the data will be always available to the client and where by shared resources, software and information are provided by the service providers on demand. It means in cloud computing is done by migrating local data management systems into cloud servers, users can enjoy high quality services and save significant investments on their local infrastructure. Cloud computing is very attractive environment for business world in terms of cost and providing services. Cloud computing is long dreamed vision of computing as a utility where data owners can remotely store their data in a cloud to enjoy on demand high quality applications and services from a shared pool of configurable computing resources. Advantages and disadvantages of cloud computing Advantages: Location independent Easy maintenance Secure storage and management High level computing Disadvantages: Lack of control Security and privacy Higher operational cost Reliability 2.RELATED WORK In 2003, Kallahalla proposed a system named PLUTUS enables the secure file sharing on the un trusted cloud servers by using the cryptographic storage system. In this method, the files are divided into the file groups and encrypting each group with a unique file block key. Now the data owner can share the file groups with the others by delivering the corresponding lock box keys, where the lock box key is used for encrypting the file-block keys. But this brings a heavy key distribution for the large amounts of file sharing and more additionally the file-block keys need to be updated every time when ever the user revocation occurs and the updated keys has to be distributed. In 2003, the E.Goh and his team proposed a system named “sirius”. In that the files stored on the untrusted server include two parts: file metadata and file data. In the file meta data it include a series of encrypted key blocks and each one is encrypted by the public key of the authorized users. Here also the user revocation is an intractable issue for the large-scale file sharing. Since every time the file’s meta data also need to be updated. In the next version , the NNL construction is used for the efficient key revocation .But in this also whenever a new user joins in the group, there is no need to recomputed the private keys of the every user. In 2005, ateniese et.al proposed the proxy re encryptions for the secure distributed storage. Here in this the concept of encryption computation overhead increases with the data sharing rate. In this the data owner encrypts the data with the two types of keys like unique and symmetric content keys. These two keys are further encrypted by a master public key. Here for the access control, the server uses proxy cryptography to directly re encrypt the keys with the master public key granted user’s public key. But when any revoked users can be launched they will be able to learn the decryption keys. In 2010,Yu.et.al proposed a scalable and fine grained data access control scheme in the cloud computing by using the KP-ABE technique. In this scheme, the data owners encrypt the file with a rand key where this random key is further encrypted with a group of attributes y using the KP-ABE and the respected secret keys to the authorized users, then the user can only decrypt the cipher text if the data file attributes match with the access structure. To achieve the user revocation the cloud servers takes the responsibility from manager of the tasks such as file re encryption and the secret key updates. Here in this scenario, the single owner manner may create the problem with the implementation of applications where all the users can share data with the others. In 2010 the Lu.et.al proposed the secure provenance scheme. In this they implemented the group signatures and the cipher text policy ABE techniques. In this scheme the system is set with a single attribute. In this method the user gets two keys after the registration. The two keys are group signature key and the remaining users in the same group can decrypt the data with their group signature key for the privacy preserving and traceability. But in this scheme the user revocation is not presented. By Observing all this analysis we have a greater challenging issue that is how we can securely share data with the others by the multiple-owner manner for the dynamic groups in the un trusted cloud along with T.Vijayalakshmi et al, / (IJCSIT) International Journal of Computer Science and Information Technologies, Vol. 6 (4) , 2015, 3577-3580
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