Biblio

Data sharing is a significant functionality in cloud storage. These cloud storage provider are answerable for keeping the data obtainable and available in addition to the physical environment protected and running. Here we can securely, efficiently, and flexibly share data with others in cloud storage. A new public-key cryptosystems is planned which create constant-size cipher texts such that efficient allocation of decryption rights for any set of cipher texts are achievable. The uniqueness means that one can aggregate any set of secret keys and make them as packed in as a single key, but encircling the power of all the keys being aggregated. This packed in aggregate key can be easily sent to others or be stored in a smart card with very restricted secure storage. In KAC, users encrypt a file with single key, that means every file have each file, also there will be aggregate keys for two or more files, which formed by using the tree structure. Through this, the user can share more files with a single key at a time.