@misc{cryptoeprint:2004:148,
    author = {Zuowen Tan and Zhuojun Liu},
    title = {Provably Secure Delegation-by-Certification Proxy Signature Schemes},
    howpublished = {Cryptology ePrint Archive, Report 2004/148},
    year = {2004},
    url = {http://eprint.iacr.org/2004/148},
}