@misc{cryptoeprint:2011:206,
author = {R. Farashahi and D. Moody and H. Wu},
title = {Isomorphism classes of Edwards curves over finite fields},
howpublished = {Cryptology ePrint Archive, Report 2011/206},
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.