Cryptology ePrint Archive: BibTeX Citation of Report 2015/685

@misc{cryptoeprint:2015:685,
    author = {Robert Granger and Thorsten Kleinjung and Jens Zumbr\"agel},
    title = {On the discrete logarithm problem in finite fields of fixed characteristic},
    howpublished = {Cryptology ePrint Archive, Report 2015/685},
    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.