Nam-Su Jho Eun Sun Yoo Jung Hee Cheon Myung-Hwan Kim New broadcast encryption scheme using tree-based circle. 37-44 2005 conf/drm/2005 Digital Rights Management Workshop http://doi.acm.org/10.1145/1102546.1102554 db/conf/drm/drm2005.html#JhoYCK05