Jan Camenisch Maciej Koprowski Bogdan Warinschi Efficient Blind Signatures Without Random Oracles. 134-148 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3352&spage=134 2004 conf/scn/2004 SCN db/conf/scn/scn2004.html#CamenischKW04