Efficient public key cryptosystem for scalable data sharing in Cloud storage

The Cloud storage means the storing the data online in the form of cloud. Data sharing is one of the important functionality in cloud. This approach describe one of the public-key cryptosystems as Key Aggregate Cryptosystem. This cryptosystem produce constant-size cipher texts, here decryption is more powerful since any set of cipher text can be decrypted at only one time by using aggregate key. which will show how one can communicate or share the data from cloud securely, efficiently and flexibly. The concept of this cryptosystem is that one can aggregate or gather any set of secret keys and from that gathering keys make single key which is compact. That means, the user who hold the secret key can send a constant-size aggregate key for set of cipher text in cloud, but the other encrypted files which is present outside the set will remain confidential. In this approach MES-2 that is Modern Encryption Standard-2 algorithm will be used for encryption and PKI (Public Key Infrastructure) is used for key generation.MES-2 used vernam cipher concept to encrypt the data.