@misc{cryptoeprint:2003:175,
author = {David Naccache},
title = {Double-Speed Safe Prime Generation},
howpublished = {Cryptology ePrint Archive, Report 2003/175},
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.