Sherman S. M. Chow Volker Roth Eleanor G. Rieffel General Certificateless Encryption and Timed-Release Encryption. 126-143 2008 SCN http://dx.doi.org/10.1007/978-3-540-85855-3_9 conf/scn/2008 db/conf/scn/scn2008.html#ChowRR08