Cunsheng Ding Valtteri Niemi Ari Renvall Arto Salomaa TWOPRIME: A Fast Stream Ciphering Algorithm. 88-102 http://link.springer.de/link/service/series/0558/bibs/1267/12670088.htm 1997 conf/fse/1997 FSE db/conf/fse/fse97.html#DingNRS97