@misc{cryptoeprint:2004:058,
author = {Michael Scott and Paulo S.L.M Barreto},
title = {Generating more MNT elliptic curves},
howpublished = {Cryptology ePrint Archive, Report 2004/058},
year = {2004},
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.