@misc{cryptoeprint:2013:787,
author = {Raghuvir Songhela and Manik Lal Das},
title = {Wide-weak Privacy Preserving RFID Mutual Authentication Protocol},
howpublished = {Cryptology ePrint Archive, Report 2013/787},
year = {2013},
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.