Cryptology ePrint Archive: BibTeX Citation of Report 2009/186

@misc{cryptoeprint:2009:186,
    author = {Nicolas T. Courtois and Gregory V. Bard and Shaun V. Ault},
    title = {Statistics of Random Permutations and the Cryptanalysis of Periodic Block Ciphers },
    howpublished = {Cryptology ePrint Archive, Report 2009/186},
    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.