@misc{cryptoeprint:2003:055,
author = {Xiaofeng Chen and Fangguo Zhang and Yumin Wang},
title = {A New Approach to Prevent Blackmailing in E-Cash},
howpublished = {Cryptology ePrint Archive, Report 2003/055},
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.