Cryptology ePrint Archive: BibTeX Citation of Report 2006/215

@misc{cryptoeprint:2006:215,
    author = {Shujun Li and Chengqing Li and Kowk-Tung Lo and Guanrong Chen},
    title = {Cryptanalysis of an Image Scrambling Scheme without Bandwidth Expansion},
    howpublished = {Cryptology ePrint Archive, Report 2006/215},
    year = {2006},
    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.