Key Aggregate Cryptosystem Data Sharing in Cloud Storage

To securely, efficiently, and flexibly share data with others in cloud storage, we describe new public-key cryptosystems which produce constant-size cipher texts such that efficient delegation of decryption rights for any set of cipher texts are possible. The novelty is that one can aggregate any set of secret keys and make them as compact as a single key. The secret key holder can release a constant-size aggregate key for flexible choices of cipher text set in cloud storage, but the other encrypted files outside the set remain confidential.