Cryptology ePrint Archive: BibTeX Citation of Report 2011/563

@misc{cryptoeprint:2011:563,
    author = {Masoumeh Safkhani and  Nasour Bagheri  and Majid Naderi},
    title = {On the Security of RFID Anti Cloning Security Protocol(ACSP)},
    howpublished = {Cryptology ePrint Archive, Report 2011/563},
    year = {2011},
    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.