@misc{cryptoeprint:2006:479,
    author = {Alfredo De Santis and Anna Lisa Ferrara and Barbara Masucci},
    title = {Efficient Provably-Secure Hierarchical Key Assignment Schemes},
    howpublished = {Cryptology ePrint Archive, Report 2006/479},
    year = {2006},
    url = {http://eprint.iacr.org/2006/479},
}