@misc{cryptoeprint:2008:185,
author = {Di Ma and Gene Tsudik},
title = {A New Approach to Secure Logging},
howpublished = {Cryptology ePrint Archive, Report 2008/185},
year = {2008},
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.