@misc{cryptoeprint:2006:226,
author = {Guilin Wang, Feng Bao, and Jianying Zhou},
title = {The Fairness of Perfect Concurrent Signatures},
howpublished = {Cryptology ePrint Archive, Report 2006/226},
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.