Cryptology ePrint Archive: BibTeX Citation of Report 2012/169

@misc{cryptoeprint:2012:169,
    author = {Xiaopei Guo,  Kejian Xu,  Tongsen Sun and  Xiubin Fan},
    title = {Analysis of Minimum  Numbers of Linearly  Active S-Boxes of a Class of Generalized Feistel Block Ciphers},
    howpublished = {Cryptology ePrint Archive, Report 2012/169},
    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.