Kaoru Kurosawa Jun Furukawa Universally Composable Undeniable Signature. 524-535 2008 ICALP (2) http://dx.doi.org/10.1007/978-3-540-70583-3_43 conf/icalp/2008-2 db/conf/icalp/icalp2008-2.html#KurosawaF08