Data sharing is an essential practicality in cloud storage. In this paper, the authors have a tendency to show a way to firmly, diligently and flexibly share knowledge with others in cloud storage. They have a tendency to describe new public-key cryptosystems which manufacture constant-size cipher texts specified economical delegation of cryptography rights for any set of cipher texts are potential. The novelty is that one will combination any set of secret keys and build them as compact as one key, however enveloping the facility of all the keys being aggregative. In different words, the key holder will unleash a constant-size combination key for versatile decisions of cipher text set in cloud storage, yet the opposite encrypted files outside the set stay confidential.