Cryptology ePrint Archive: BibTeX Citation of Report 2004/087

@misc{cryptoeprint:2004:087,
    author = {K. Rubin and A. Silverberg},
    title = {Using primitive subgroups to do more with fewer bits},
    howpublished = {Cryptology ePrint Archive, Report 2004/087},
    year = {2004},
    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.