Cryptology ePrint Archive: BibTeX Citation of Report 2015/847

@misc{cryptoeprint:2015:847,
    author       = {Subhadeep Banik and
		    Andrey Bogdanov and
		    Francesco Regazzoni},
    title        = {Exploring Energy Efficiency of Lightweight Block Ciphers},
    howpublished = {Cryptology ePrint Archive, Report 2015/847},
    year         = {2015},
    note         = {\url{https://ia.cr/2015/847}},
}

You will need the url.sty package (comes with most LaTeX installations) for the last line. Otherwise, remove the \url command.