Cryptology ePrint Archive: BibTeX Citation of Report 2013/635

@misc{cryptoeprint:2013:635,
    author = {Arjen K. Lenstra, Thorsten Kleinjung, Emmanuel Thomé},
    title = {Universal security; from bits and mips to pools, lakes -- and beyond},
    howpublished = {Cryptology ePrint Archive, Report 2013/635},
    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.