Goichiro Hanaoka Junji Shikata Yumiko Hanaoka Hideki Imai Unconditionally Secure Anonymous Encryption and Group Authentication. 81-99 2002 conf/asiacrypt/2002 ASIACRYPT http://link.springer.de/link/service/series/0558/bibs/2501/25010081.htm db/conf/asiacrypt/asiacrypt2002.html#HanaokaSHI02