@misc{cryptoeprint:2004:125,
author = {Shai Halevi},
title = {EME*: extending EME to handle arbitrary-length messages with associated data},
howpublished = {Cryptology ePrint Archive, Report 2004/125},
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.