Heasuk Jo Woongryul Jeon Yunho Lee Seungjoo Kim Dongho Won Security Specification for Conversion Technologies of Heterogeneous DRM Systems. 159-170 2009 ISPEC http://dx.doi.org/10.1007/978-3-642-00843-6_15 conf/ispec/2009 db/conf/ispec/ispec2009.html#JoJLKW09