Cryptology ePrint Archive: BibTeX Citation of Report 2012/214

@misc{cryptoeprint:2012:214,
    author = {Shengbao Wu and Mingsheng Wang},
    title = {Automatic Search of Truncated Impossible Differentials for Word-Oriented Block Ciphers (Full Version)},
    howpublished = {Cryptology ePrint Archive, Report 2012/214},
    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.