@misc{cryptoeprint:2012:732,
author = {Eduarda S.V. Freire and Dennis Hofheinz and Eike Kiltz and Kenneth G. Paterson},
title = {Non-Interactive Key Exchange},
howpublished = {Cryptology ePrint Archive, Report 2012/732},
year = {2012},
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.