Short CCA-Secure Ciphertext-Policy Attribute-Based Encryption

We propose a technique of individually modifying an attribute-based encryption scheme (ABE) secure against chosen-plaintext attacks (CPA) into an ABE scheme secure against chosen-ciphertext attacks (CCA) in the standard model. We demonstrate the technique in the case of the Waters ciphertext-policy ABE (CP-ABE). Our technique is helpful when a Diffie-Hellman tuple to be verified is in the terminal group of a bilinear map. We utilize the Twin Diffie-Hellman Trapdoor Test of Cash, Kiltz and Shoup, and it results in expansion of secret key length and decryption cost of computation by a factor of four, whereas public key length, ciphertext length and encryption cost of computation remain almost the same. In the case that the size of attribute sets are small, those lengths and costs are smaller than those of the CP-ABE obtained via the generic transformation of Yamada et al. in PKC 2011.