@misc{cryptoeprint:2013:591,
author = {Jung Woo Kim and Jin Hong and Kunsoo Park},
title = {Analysis of the Rainbow Tradeoff Algorithm Used in Practice},
howpublished = {Cryptology ePrint Archive, Report 2013/591},
year = {2013},
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.