@misc{cryptoeprint:2010:657,
author = {Yasufumi Hashimoto},
title = {On small secret key attack against RSA with high bits known prime factor},
howpublished = {Cryptology ePrint Archive, Report 2010/657},
year = {2010},
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.