Cryptology ePrint Archive: BibTeX Citation of Report 2004/172

@misc{cryptoeprint:2004:172,
    author = {Dan Boneh and Xavier Boyen},
    title = {Efficient Selective-ID Secure Identity Based Encryption Without Random Oracles},
    howpublished = {Cryptology ePrint Archive, Report 2004/172},
    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.