Anonymous Constant-Size Ciphertext HIBE from Asymmetric Pairings

We present a new hierarchical identity based encryption (HIBE) scheme with constant-size ciphertext that can be implemented using the most efficient bilinear pairings, namely, Type-3 pairings. In addition to being fully secure, our scheme is anonymous. The HIBE is obtained by extending an asymmetric pairing based IBE scheme due to Lewko and Waters. The extension uses the approach of Boneh-Boyen-Goh to obtain constant-size ciphertexts and that of Boyen-Waters for anonymity. Security argument is based on the dual-system technique of Waters. The resulting HIBE is the only known scheme using Type-3 pairings achieving constant-size ciphertext, security against adaptive-identity attacks and anonymity under static assumptions without random oracles.