@misc{cryptoeprint:2004:295,
    author = {Jiang Wu and Ruizhong Wei},
    title = {An Access Control Scheme for Partially Ordered Set Hierarchy with Provable Security},
    howpublished = {Cryptology ePrint Archive, Report 2004/295},
    year = {2004},
    url = {http://eprint.iacr.org/2004/295},
}