Cryptology ePrint Archive: BibTeX Citation of Report 2012/689

@misc{cryptoeprint:2012:689,
    author = {Abishek Kumarasubramanian and Rafail Ostrovsky and Omkant Pandey and Akshay Wadia},
    title = {Cryptography Using CAPTCHA Puzzles},
    howpublished = {Cryptology ePrint Archive, Report 2012/689},
    year = {2012},
    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.