@misc{cryptoeprint:2009:163,
author = {Bjoern Grohmann},
title = {A New Key-Agreement-Protocol},
howpublished = {Cryptology ePrint Archive, Report 2009/163},
year = {2009},
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.