@misc{cryptoeprint:2001:081,
    author = {Masao Mori},
    title = {A Sufficient Condition for Secure Ping--Pong Protocols},
    howpublished = {Cryptology ePrint Archive, Report 2001/081},
    year = {2001},
    url = {http://eprint.iacr.org/2001/081},
}