Cryptology ePrint Archive: BibTeX Citation of Report 2012/042

@misc{cryptoeprint:2012:042,
    author = {Naoyuki Shinohara and Takeshi Shimoyama and Takuya Hayashi and Tsuyoshi Takagi },
    title = {Key Length Estimation of Pairing-based Cryptosystems using $\eta_T$ Pairing},
    howpublished = {Cryptology ePrint Archive, Report 2012/042},
    year = {2012},
    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.