@misc{cryptoeprint:2004:052,
    author = {Tal Malkin and Satoshi Obana and Moti Yung},
    title = {The Hierarchy of Key Evolving Signatures and a Characterization of Proxy Signatures},
    howpublished = {Cryptology ePrint Archive, Report 2004/052},
    year = {2004},
    url = {http://eprint.iacr.org/2004/052},
}