Sangwon Lee Yongdae Kim Kwangjo Kim DaeHyun Ryu An Efficient Tree-Based Group Key Agreement Using Bilinear Map. 357-371 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2846&spage=357 2003 conf/acns/2003 ACNS db/conf/acns/acns2003.html#LeeKKR03