A DFA-based functional proxy re-encryption scheme for secure public cloud data sharing
In this paper for the first time we define a general notion for Proxy Re-Encryption (PRE), which we call Deterministic Finite Automata Based Functional PRE (DFA-based FPRE). Meanwhile, we propose the first and concrete DFA-based FPRE system which adapts to our new notion. In our scheme a message is encrypted in a ciphertext associated with an arbitrary length index string, and a decryptor is legitimate if and only if a DFA associated with his/her secret key accepts the string. Furthermore, the above encryption is allowed to be transformed to another ciphertext associated with a new string by a semi-trusted proxy whom is given a re-encryption key. Nevertheless, the proxy cannot gain access to the underlying plaintext. This new primitive can increase the flexibility of users to delegate their decryption rights to others. We also prove it fully chosen-ciphertext secure in the standard model.