Cryptology ePrint Archive: BibTeX Citation of Report 2015/865

@misc{cryptoeprint:2015:865,
    author = {Alexander Koch and Stefan Walzer and Kevin Härtel},
    title = {Card-based Cryptographic Protocols Using a Minimal Number of Cards},
    howpublished = {Cryptology ePrint Archive, Report 2015/865},
    year = {2015},
    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.