Abstract: Data sharing is a crucial functionality in cloud storage. With the current wireless technology and the usage of different smart devices, the sharing of data has become very easy with the help of Internet. Data sharing has become an important aspect to be considered in cloud. The cloud users want their files, folders, pictures and other confidential things to be available for their utilization. It is essential to safely, productively, and adaptably impart information to others in distributed storage. A special type of public-key encryption which is called enhanced Key-Aggregation Cryptosystem is designed to outline an effective scheme that helps in flexible delegation by a constant-size decryption key. The novelty is that one can aggregate any set of secret keys and make them as compact as a single key, but encompassing the decryption power of all the keys being aggregated. In modern cryptography, a fundamental problem is leveraging the secrecy of a small piece of knowledge into the ability to perform cryptographic functions multiple times. Here the efforts are taken for making the powerful decryption key, which permits decryption of different ciphertexts without expanding the aggregate key size. This scheme also holds well in the standard model and can be applicable anytime in cloud storage.

Keywords: Cloud storage, data sharing, ciphertexts, powerful aggregate key.