Cryptology ePrint Archive: BibTeX Citation of Report 2003/090

@misc{cryptoeprint:2003:090,
    author = {Chih-Yin Lin and Tzong-Chen Wu and Fangguo Zhang},
    title = {A Structured Multisignature Scheme from the Gap Diffie-Hellman Group},
    howpublished = {Cryptology ePrint Archive, Report 2003/090},
    year = {2003},
    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.