Cryptology ePrint Archive: BibTeX Citation of Report 2009/453

@misc{cryptoeprint:2009:453,
    author = {Vlastimil Klima and Petr Susil},
    title = {A Note on Linear Approximations of BLUE MIDNIGHT WISH Cryptographic Hash Function},
    howpublished = {Cryptology ePrint Archive, Report 2009/453},
    year = {2009},
    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.