Cryptology ePrint Archive: BibTeX Citation of Report 2009/344

@misc{cryptoeprint:2009:344,
    author = {Xi Zhang and  Min-Rong Chen and Xia Li},
    title = {Comments on Shao-Cao's Unidirectional Proxy Re-Encryption Scheme  from PKC 2009},
    howpublished = {Cryptology ePrint Archive, Report 2009/344},
    year = {2009},
    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.