Yodai Watanabe Junji Shikata Hideki Imai Equivalence between Semantic Security and Indistinguishability against Chosen Ciphertext Attacks. 71-84 2003 conf/pkc/2003 Public Key Cryptography http://link.springer.de/link/service/series/0558/bibs/2567/25670071.htm db/conf/pkc/pkc2003.html#WatanabeSI03