Biblio

Inner-product encryption (IPE) is a well-known functional encryption primitive that allows decryption when the inner-product of the attribute vectors, upon which the encrypted data and the decryption key depend, is equal to zero. Using IPE, it is possible to define fine-grained access policies over encrypted data whose enforcement can be outsourced to the cloud where the data are stored. However, current IPE schemes do not support efficient access policy changes. In this paper, we propose an efficient inner-product proxy re-encryption (E-IPPRE) scheme that provides the proxy server with a transformation key, with which a ciphertext associated with an attribute vector can be transformed to a new ciphertext associated with a different attribute vector, providing a policy update mechanism with a performance suitable for many practical applications. We experimentally assess the efficiency of our protocol and show that it is selective attribute-secure against chosen-plaintext attacks in the standard model under the Asymmetric Decisional Bilinear Diffie-Hellman assumption.