Cryptology ePrint Archive: BibTeX Citation of Report 2008/428

@misc{cryptoeprint:2008:428,
    author = {Mira Belenkiy and Jan Camenisch and Melissa Chase and Markulf Kohlweiss and Anna Lysyanskaya and Hovav Shacham},
    title = {Delegatable Anonymous Credentials},
    howpublished = {Cryptology ePrint Archive, Report 2008/428},
    year = {2008},
    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.