@misc{cryptoeprint:2004:034,
author = {Gideon Samid},
title = {s(n) An Arithmetic Function of Some Interest, and Related Arithmetic},
howpublished = {Cryptology ePrint Archive, Report 2004/034},
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.