Cryptology ePrint Archive: BibTeX Citation of Report 2008/112

@misc{cryptoeprint:2008:112,
    author = {Dong Zheng and Xiangxue Li and Changshe Ma and Kefei  Chen and Jianhua Li},
    title = {Democratic Group Signatures with Threshold Traceability},
    howpublished = {Cryptology ePrint Archive, Report 2008/112},
    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.