Cryptology ePrint Archive: BibTeX Citation of Report 2011/216

@misc{cryptoeprint:2011:216,
    author = {Shaohua Tang and Lingling Xu and Niu Liu and  Jintai Ding and Zhiming Yang},
    title = {Provably Secure Group Key Management Approach Based upon Hyper-sphere},
    howpublished = {Cryptology ePrint Archive, Report 2011/216},
    year = {2011},
    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.