@misc{cryptoeprint:2001:098,
author = {Paulo S. L. M. Barreto and Hae Yong Kim},
title = {Fast hashing onto elliptic curves over fields of characteristic 3},
howpublished = {Cryptology ePrint Archive, Report 2001/098},
year = {2001},
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.