Cryptology ePrint Archive: BibTeX Citation of Report 2012/391

@misc{cryptoeprint:2012:391,
    author = {Shaohui Wang,Sujuan Liu,Danwei Chen},
    title = {Analysis and Construction of Efficient RFID Authentication Protocol with Backward Privacy},
    howpublished = {Cryptology ePrint Archive, Report 2012/391},
    year = {2012},
    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.