Cryptology ePrint Archive: BibTeX Citation of Report 2012/312

@misc{cryptoeprint:2012:312,
    author = {Debiao He},
    title = {Cryptanalysis of a Provably Secure Gateway-Oriented Password-Based Authenticated Key Exchange Protocol},
    howpublished = {Cryptology ePrint Archive, Report 2012/312},
    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.