Cryptology ePrint Archive: BibTeX Citation of Report 2008/502

@misc{cryptoeprint:2008:502,
    author = {Vanesa Daza and Javier Herranz and Paz Morillo and Carla Rafols},
    title = {Extended Access Structures and Their Cryptographic Applications},
    howpublished = {Cryptology ePrint Archive, Report 2008/502},
    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.