@misc{cryptoeprint:2004:249,
author = {Zhaohui Cheng and Richard Comley},
title = {Attacks On An ISO/IEC 11770-2 Key Establishment Protocol},
howpublished = {Cryptology ePrint Archive, Report 2004/249},
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.