Cryptology ePrint Archive: BibTeX Citation of Report 2015/580

@misc{cryptoeprint:2015:580,
    author = {Jan Camenisch and Maria Dubovitskaya and Kristiyan Haralambiev and Markulf Kohlweiss},
    title = {Composable & Modular Anonymous Credentials: Definitions and Practical Constructions},
    howpublished = {Cryptology ePrint Archive, Report 2015/580},
    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.