Shaoquan Jiang Guang Gong Multi-service Oriented Broadcast Encryption. 1-11 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3108&spage=1 2004 conf/acisp/2004 ACISP db/conf/acisp/acisp2004.html#ShaoquanG04