Cryptology ePrint Archive: BibTeX Citation of Report 2008/373

@misc{cryptoeprint:2008:373,
    author = {Fagen Li and Masaaki Shirase and Tsuyoshi Takagi },
    title = {Analysis and Improvement of Authenticatable Ring Signcryption Scheme},
    howpublished = {Cryptology ePrint Archive, Report 2008/373},
    year = {2008},
    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.