Provably secure and efficient bounded ciphertext policy attribute based encryption

Ciphertext policy attribute based encryption (CPABE) allows a sender to distribute messages based on an access policy which can be expressed as a boolean function consisting of (OR, AND) gates between attributes. A receiver whose secret key is associated with those attributes could only decrypt a ciphertext successfully if and only if his attributes satisfy the ciphertext's access policy. Fine-grained access control, a new concept mentioned by GPSW in CCS'06 can realize a more delicate access policy which could be represented as an access tree with threshold gates connecting attributes. In ICALP'08, Goyal et al. design a bounded CPABE (denoted as GJPS) with fine-grained access policy which can be proven secure under a number-theoretic assumption. In this paper, we improve their scheme by providing faster encryption / decryption algorithm and shortened ciphertext size. Moreover, we use one-time signature technique to obtain a chosen ciphertext secure extension and give its complete security proof in the standard model under traditional Decisional Bilinear Diffie-Hellman (DBDH) assumption and strong existential unforgeability of one-time signature scheme.