@misc{cryptoeprint:2003:088,
author = {A.G.Rostovtsev and E.B.Makhovenko},
title = {Elliptic Curve Point Multiplication},
howpublished = {Cryptology ePrint Archive, Report 2003/088},
year = {2003},
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.