With the ever-growing production of data coming from multiple, scattered, highly dynamical sources (like those found in IoT scenarios), many providers are motivated to upload their data to the cloud servers and share them with other persons with different purposes. However, storing data on cloud imposes serious concerns in terms of data confidentiality and access control. These concerns get more attention when data is required to be shared among multiple users with different access policies. In order to update access policy without making re-encryption, we propose an efficient inner-product proxy re-encryption scheme that provides a proxy server with a transformation key with which a delegator’s ciphertext associated with an attribute vector can be transformed to a new ciphertext associated with delegatee’s attribute vector set. Our proposed policy updating scheme enables the delegatee to decrypt the shared data with its own key without requesting a new decryption key. We experimentally analyze the efficiency of our scheme and show that our scheme is adaptive attribute-secure against chosen-plaintext under standard Decisional Linear (D-Linear ) assumption.
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