Data sharing in cloud computing is depriving user’direct control over the outsourced data, which inevitably raises
security concerns and challenges ... Another way to think of is to allow data owners to define access policies and encrypt the
sharing data with the attribute-based encryption under the access policies, only authenticated users whose attributes matching
their policies can decrypt the cipher text ... However, here also data owner needs to download, decrypt and re-encrypt the
requested data in case data access policies change dynamically and frequently.Extra computation cost and communication
overhead have been introduced to the data owner ... Another way to think of is to allow data owners to define access policies and
encrypt the sharing data with the attribute-based encryption under the access policies, only authenticated users whose attributes
matching their policies can decrypt the cipher text
