Cryptology ePrint Archive: BibTeX Citation of Report 2014/223

@misc{cryptoeprint:2014:223,
    author = {Léo Perrin and  Dmitry Khovratovich},
    title = {Collision Spectrum, Entropy Loss, T-Sponges, and Cryptanalysis of GLUON-64},
    howpublished = {Cryptology ePrint Archive, Report 2014/223},
    year = {2014},
    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.