Cryptology ePrint Archive: BibTeX Citation of Report 2015/400

@misc{cryptoeprint:2015:400,
    author = {Stephen R. Tate and Roopa Vishwanathan},
    title = {Expiration and Revocation of Keys for Attribute-based Signatures (Full Version)},
    howpublished = {Cryptology ePrint Archive, Report 2015/400},
    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.