Cryptology ePrint Archive: BibTeX Citation of Report 2012/681

@misc{cryptoeprint:2012:681,
    author = {Guang Gong and Mark Aagaard and Xinxin Fan},
    title = {Resilience to Distinguishing Attacks on WG-7 Cipher and Their Generalizations},
    howpublished = {Cryptology ePrint Archive, Report 2012/681},
    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.