Cryptology ePrint Archive: BibTeX Citation of Report 2015/433

@misc{cryptoeprint:2015:433,
    author = {Wentao Zhang and. Zhenzhen Bao and. Vincent Rijmen and. Meicheng Liu},
    title = {A New Classification of 4-bit Optimal S-boxes and its Application to PRESENT, RECTANGLE and SPONGENT},
    howpublished = {Cryptology ePrint Archive, Report 2015/433},
    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.