Ratna Dutta Rana Barua Palash Sarkar Provably Secure Authenticated Tree Based Group Key Agreement. 92-104 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3269&spage=92 2004 conf/icics/2004 ICICS db/conf/icics/icics2004.html#DuttaBS04