@misc{cryptoeprint:2004:270,
author = {Fuw-Yi Yang and Jinn-Ke Jan},
title = {An Enhanced and Secure Protocol for Authenticated Key Exchange},
howpublished = {Cryptology ePrint Archive, Report 2004/270},
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.