Cryptology ePrint Archive: BibTeX Citation of Report 2013/561

@misc{cryptoeprint:2013:561,
    author = {Pawel Morawiecki and Josef Pieprzyk and Marian Srebrny and Michal Straus},
    title = {Preimage attacks on the round-reduced Keccak with the aid of differential cryptanalysis},
    howpublished = {Cryptology ePrint Archive, Report 2013/561},
    year = {2013},
    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.