@misc{cryptoeprint:2008:447,
author = {Chong-zhi Gao and Baodian Wei and Dongqing Xie and Chunming Tang},
title = {Divisible On-line/Off-line Signatures},
howpublished = {Cryptology ePrint Archive, Report 2008/447},
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.