Cryptology ePrint Archive: BibTeX Citation of Report 2013/238

@misc{cryptoeprint:2013:238,
    author = {Markulf Kohlweiss and Ueli Maurer and Cristina Onete and Björn Tackmann and Daniele Venturi},
    title = {Anonymity-preserving Public-Key Encryption: A Constructive Approach},
    howpublished = {Cryptology ePrint Archive, Report 2013/238},
    year = {2013},
    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.