Cryptology ePrint Archive: BibTeX Citation of Report 2004/109

@misc{cryptoeprint:2004:109,
    author = {Robert Bradshaw and Jason Holt and Kent Seamons},
    title = {Concealing Complex Policies with Hidden Credentials},
    howpublished = {Cryptology ePrint Archive, Report 2004/109},
    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.