@misc{cryptoeprint:2011:008,
author = {Ping Wang and Fangguo Zhang},
title = {Computing Elliptic Curve Discrete Logarithms with the Negation Map},
howpublished = {Cryptology ePrint Archive, Report 2011/008},
year = {2011},
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.