Cryptology ePrint Archive: BibTeX Citation of Report 2015/921

@misc{cryptoeprint:2015:921,
    author = {Kwangsu Lee and Jong Hwan Park},
    title = {Identity-Based Revocation from Subset Difference Methods under Simple Assumptions},
    howpublished = {Cryptology ePrint Archive, Report 2015/921},
    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.