Group Signatures with Separate and Distributed Authorities.

Jun Furukawa Shoko Yonezawa Group Signatures with Separate and Distributed Authorities. 77-90 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3352&spage=77 2004 conf/scn/2004 SCN db/conf/scn/scn2004.html#FurukawaY04