Cryptology ePrint Archive: BibTeX Citation of Report 2015/275

@misc{cryptoeprint:2015:275,
    author = {Takanori Yasuda and Xavier Dahan and Yun-Ju Huang and Tsuyoshi Takagi and Kouichi Sakurai},
    title = {MQ Challenge: Hardness Evaluation of Solving Multivariate Quadratic Problems},
    howpublished = {Cryptology ePrint Archive, Report 2015/275},
    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.