Cryptology ePrint Archive: BibTeX Citation of Report 2003/255

@misc{cryptoeprint:2003:255,
    author = {Peter Fairbrother},
    title = {Improved Constructions for Universal Re-encryption.},
    howpublished = {Cryptology ePrint Archive, Report 2003/255},
    year = {2003},
    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.