@misc{cryptoeprint:2011:035,
author = {Andrew C. Yao and Yunlei Zhao},
title = {A New Family of Implicitly Authenticated Diffie-Hellman Protocols},
howpublished = {Cryptology ePrint Archive, Report 2011/035},
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.