@misc{cryptoeprint:2005:176,
author = {Hugo Krawczyk},
title = {HMQV: A High-Performance Secure Diffie-Hellman Protocol },
howpublished = {Cryptology ePrint Archive, Report 2005/176},
year = {2005},
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.