Christophe Debaert Henri Gilbert The RIPEMD and RIPEMD Improved Variants of MD4 Are Not Collision Free. 52-65 2001 conf/fse/2001 FSE http://link.springer.de/link/service/series/0558/bibs/2355/23550052.htm db/conf/fse/fse2001.html#DebaertG01