Shiho Moriai Takeshi Shimoyama Toshinobu Kaneko Higher Order Differential Attak of CAST Cipher. 17-31 http://link.springer.de/link/service/series/0558/bibs/1372/13720017.htm 1998 conf/fse/1998 FSE db/conf/fse/fse98.html#MoriaiSK98