Alex Biryukov Analysis of Involutional Ciphers: Khazad and Anubis. 45-53 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2887&spage=45 2003 conf/fse/2003 FSE db/conf/fse/fse2003.html#Biryukov03