Jian Weng Robert H. Deng Xuhua Ding Cheng-Kang Chu Junzuo Lai Conditional proxy re-encryption secure against chosen-ciphertext attack. 322-332 2009 ASIACCS http://doi.acm.org/10.1145/1533057.1533100 conf/ccs/2009asia db/conf/ccs/asiaccs2009.html#WengDDCL09