Cloud computing is a set of different types of hardware and software activities that work collectively to deliver many aspects of computing to the end user as an online services. It provides on demand scalable and cost effective services for storing documents. However with all of these features it enters with number of challenges associated in utilizing the cloud securely. Achieving unbreakable document or outsourced data security is an important issue to consider. For this purpose encryption has been suggested, with the popularity of using cryptography to store data in the cloud Attribute Based Encryption receives widespread attention of the researchers. Also to provide security to the outsourced documents, Attribute based encryption is an excellent solution. On the other side of cloud environment, to increase productivity of the cloud, collaboration with more users is important. But the encryption limits the admission of newly authorized user to acquire the data because, when the ciphertext is need to be share with others legally there will be necessity of extending an original access policy specified in ABE. In this process, at the time of extending policy, data uploader had to download ciphertext, modify the access policy as per current requirement and then reupload the data with modified access permissions. This significantly increases the processing time to extend access policy and consumes server space unnecessarily. To address above problem we have introduce modified attribute based encryption with time varying encryption scheme for document encryption which is based on the research of Time Varying Camellia Encryption Algorithm for the cloud storage environment and a novel solution for access permission management in which we will use metadata file to store access permission. Finally we discuss the evaluation result made in between existing work and proposed system.

Time varying encryption, Extended Access Control, Collaboration in cloud, Attribute Based Encryption

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