Cryptology ePrint Archive: BibTeX Citation of Report 2012/310

@misc{cryptoeprint:2012:310,
    author = {Koji Nuida and Takuro Abe and Shizuo Kaji and Toshiaki Maeno and Yasuhide Numata},
    title = {A mathematical problem for security analysis of hash functions and pseudorandom generators},
    howpublished = {Cryptology ePrint Archive, Report 2012/310},
    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.