Zvika Brakerski Shafi Goldwasser Guy N. Rothblum Vinod Vaikuntanathan Weak Verifiable Random Functions. 558-576 2009 TCC http://dx.doi.org/10.1007/978-3-642-00457-5_33 conf/tcc/2009 db/conf/tcc/tcc2009.html#BrakerskiGRV09