Shanshan Duan Zhenfu Cao Yuan Zhou Secure Delegation-by-Warrant ID-Based Proxy Signcryption Scheme. 445-450 2005 conf/cis/2005-2 CIS (2) http://dx.doi.org/10.1007/11596981_65 db/conf/cis/cis2005-2.html#DuanCZ05