Cryptology ePrint Archive: BibTeX Citation of Report 2015/122

@misc{cryptoeprint:2015:122,
    author = {Siwei Sun, Lei Hu, Meiqin Wang, Peng Wang, Kexin Qiao, Xiaoshuang Ma, Danping Shi, Ling Song, Kai Fu},
    title = {Constructing Mixed-integer Programming Models whose Feasible Region is Exactly the Set of All Valid Differential Characteristics of SIMON},
    howpublished = {Cryptology ePrint Archive, Report 2015/122},
    year = {2015},
    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.