@misc{cryptoeprint:2005:407,
author = {Guomin Yang and Duncan S. Wong and Xiaotie Deng and Huaxiong Wang},
title = {Anonymous Signature Schemes},
howpublished = {Cryptology ePrint Archive, Report 2005/407},
year = {2005},
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.