Cryptology ePrint Archive: BibTeX Citation of Report 2012/581

@misc{cryptoeprint:2012:581,
    author = {Ding Wang and Chun-guang Ma},
    title = {On the (in)security of some smart-card-based password authentication schemes for WSN},
    howpublished = {Cryptology ePrint Archive, Report 2012/581},
    year = {2012},
    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.