Olivier Baudron David Pointcheval Jacques Stern Extended Notions of Security for Multicast Public Key Cryptosystems. 499-511 http://link.springer.de/link/service/series/0558/bibs/1853/18530499.htm 2000 conf/icalp/2000 ICALP db/conf/icalp/icalp2000.html#BaudronPS00