Cryptology ePrint Archive: BibTeX Citation of Report 2007/380

@misc{cryptoeprint:2007:380,
    author = {Francois Arnault, Thierry P. Berger, Cédric Lauradoux and Marine Minier},
    title = {X-FCSR: a new software oriented stream cipher based upon FCSRs},
    howpublished = {Cryptology ePrint Archive, Report 2007/380},
    year = {2007},
    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.