Cryptology ePrint Archive: BibTeX Citation of Report 2013/159

@misc{cryptoeprint:2013:159,
    author = {Dingding Jia and Bao Liand Yamin Liu and Qixiang Mei},
    title = {Improving the Message-ciphertext Rate of Lewko's Fully Secure IBE Scheme},
    howpublished = {Cryptology ePrint Archive, Report 2013/159},
    year = {2013},
    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.