An Optimised Key cryptography for Securing Cloud Data Sharing and Storage Environment

Cloud computing technology is widely used so that the data can be outsourced on cloud can accessed easily. Different members can share that data through different virtual machines but present on single physical machine. But the thing is user dont have physical control over the outsourced data. The need is to share data securely among users. The cloud service provider and users authentication is necessary to make sure no loss or leak of users data. Privacy preserving in cloud is important make sure the users identity is not revealed to everyone. On cloud anyone can share data as much they want to i. e. only selected content can be shared. Cryptography helps the data owner to share the data to in safe way. So user encrypts data and uploads on server. Different encryption and decryption keys are generated for different data. The encryption and decryption keys may be different for different set of data. Only those set of decryption keys are shared that the selected data can be decrypted. Here a public-key cryptosystems which generate a ciphertext which is of constant size. So that to transfer the decryption rules for number of ciphertext. The difference is one can collect a set of secret keys and make them as small size as a single key with holding the same ability of all the keys that are formed in a group. This compact aggregate key can be efficiently sent to others or to be stored in a smart card with little secure storage.