Yongliang Liu Xiaolin Yang Hongxun Yao Wen Gao Novel Secure Communication Protocol for Conditional Access System. 121-127 2007 5 I. J. Network Security 2 http://ijns.femto.com.tw/contents/ijns-v5-n2/ijns-2007-v5-n2-p121-127.pdf db/journals/ijnsec/ijnsec5.html#LiuYYG07