Cryptology ePrint Archive: BibTeX Citation of Report 2015/810

@misc{cryptoeprint:2015:810,
    author = {Michele Ciampi and Giuseppe Persiano and Alessandra Scafuro and Luisa Siniscalchi and Ivan Visconti},
    title = {Improved OR Composition of Sigma-Protocols},
    howpublished = {Cryptology ePrint Archive, Report 2015/810},
    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.