@misc{cryptoeprint:2015:642,
author = {Muhammed F. Esgin and Mehmet S. Kiraz and Osmanbey Uzunkol},
title = {A New Partial Key Exposure Attack on Multi-power RSA},
howpublished = {Cryptology ePrint Archive, Report 2015/642},
year = {2015},
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.