Cryptology ePrint Archive: BibTeX Citation of Report 2015/244

@misc{cryptoeprint:2015:244,
    author = {Jeremy Jean and Ivica Nikolic},
    title = {Internal Differential Boomerangs: Practical Analysis of the Round-Reduced Keccak-f Permutation},
    howpublished = {Cryptology ePrint Archive, Report 2015/244},
    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.