Akira Numayama Toshiyuki Isshiki Keisuke Tanaka Security of Digital Signature Schemes in Weakened Random Oracle Models. 268-287 2008 Public Key Cryptography http://dx.doi.org/10.1007/978-3-540-78440-1_16 conf/pkc/2008 db/conf/pkc/pkc2008.html#NumayamaIT08