@misc{cryptoeprint:2004:167,
author = {Fuw-Yi Yang and Jinn-Ke Jan},
title = {A Secure and Efficient Key Exchange Protocol for Mobile Communications},
howpublished = {Cryptology ePrint Archive, Report 2004/167},
year = {2004},
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.