Cryptology ePrint Archive: BibTeX Citation of Report 1996/007

@misc{cryptoeprint:1996:007,
    author = {Moni Naor and Adi Shamir},
    title = {Visual Cryptography II: Improving the Contrast Via the Cover Base},
    howpublished = {Cryptology ePrint Archive, Report 1996/007},
    year = {1996},
    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.