Abstract: Cloud storage in simple terms is nothing but storing data on-line in cloud that can be accessed from multiple and connected resources. Using cloud to store the data is a very practical thought as we can share our information in trustworthy domain, with great efficiency, Besides that it provides some other functionalities in terms of disaster recovery, smart accessibility etc. New public–key cryptography is presented that came out to be Key aggregate cryptosystem (KAC), in which constant size ciphertexts are produced in order to make the task of rendering the decryption rights feasible for produced mass of ciphertexts. KAC comprises the thought of integrating different keys generated for different sets of ciphertext which yields a single aggregate key accommodating power of all the keys. After which a single key can be released to someone in trusted domain through a secure channel and using this key one can decrypt set of allowed files only, others remaining unaddressed.
Keywords: Cloud storage, Data sharing, Ciphertext, Key-aggregate, Encryption.