Deukjo Hong Jaechul Sung Shiho Moriai Sangjin Lee Jongin Lim Impossible Differential Cryptanalysis of Zodiac. 300-311 2001 conf/fse/2001 FSE http://link.springer.de/link/service/series/0558/bibs/2355/23550300.htm db/conf/fse/fse2001.html#HongSMLL01