@misc{cryptoeprint:2003:067,
author = {Javier Herranz and Germ\'an S\'aez},
title = {Forking Lemmas in the Ring Signatures' Scenario},
howpublished = {Cryptology ePrint Archive, Report 2003/067},
year = {2003},
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.