@misc{cryptoeprint:2006:337,
author = {D.R. Stinson and J. Wu},
title = {An Efficient and Secure Two-flow Zero-Knowledge Identification Protocol},
howpublished = {Cryptology ePrint Archive, Report 2006/337},
year = {2006},
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.