@misc{cryptoeprint:2008:297,
author = {Hongzhen Du and Qiaoyan Wen},
title = {Attack on Kang et al.'s Identity-Based Strong Designated Verifier Signature Scheme},
howpublished = {Cryptology ePrint Archive, Report 2008/297},
year = {2008},
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.