Cryptology ePrint Archive: BibTeX Citation of Report 1997/015

@misc{cryptoeprint:1997:015,
    author = {N. Asokan, V. Shoup, M. Waidner},
    title = {Optimistic fair Exchange of Digital Signatures},
    howpublished = {Cryptology ePrint Archive, Report 1997/015},
    year = {1997},
    note = {\url{http://eprint.iacr.org/}},
}

You will need the url.sty package (comes with most LaTeX installations) for the last line. Otherwise, remove the \url command.