Cryptology ePrint Archive: BibTeX Citation of Report 2008/223

@misc{cryptoeprint:2008:223,
    author = {Bert W. Leung and Felix Y. Ng and Duncan S. Wong},
    title = {On the Security of a Visual Cryptography Scheme for Color Images},
    howpublished = {Cryptology ePrint Archive, Report 2008/223},
    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.