Cloud computing has been envisioned as the next-generation architecture of IT activity. In difference to established solution, wherever the IT services are under appropriate physical, logical and personnel controls, cloud computing moves the appliance software and databases to the large data centers, wherever the management of the data and services may not be fully reliable.This unique attribute, however, poses many new security challenges which have not been well understood. In this project, focus on cloud data storage security, which has constantly been an important feature of quality of service Data owner's stores encrypted data in the cloud to ensure security for his data in the cloud computing environment and issues decryp- tion key to only authorized user to access the data from cloud. As user is revoked, data owner has to re-encrypt the data so that revoked user cannot access the data again .To perform this operation data owner will issue re-encryption command to cloud so that data in cloud gets re-encrypted. Once re- encryption is done here is a need for generation of new decryption keys to legal user, so that they can go on to access the data. Within a cloud compu- ting environment all such commands may not be received and executed by all of the cloud servers due to unreliable network communications. To solve this problem we are proposing time-based re-encryption scheme. In this method automatic re-encryption of data will takes place based on the internal clock value present at the cloud server. To execute this automatic re-encryption we will make use of encryption technique called Attribute Based Encryption (ABE) with DES (Data Encryption Standard). ABE provides fine -grain access control and easier user revoking system and DES will provide Encryption technique.
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