@misc{cryptoeprint:2006:225,
    author = {Giuseppe Ateniese and Alfredo De Santis and Anna Lisa Ferrara and Barbara Masucci},
    title = {Provably-Secure Time-Bound Hierarchical Key Assignment Schemes},
    howpublished = {Cryptology ePrint Archive, Report 2006/225},
    year = {2006},
    url = {http://eprint.iacr.org/2006/225},
}