@misc{cryptoeprint:2008:080,
author = {Aniket Kate and Greg Zaverucha and Ian Goldberg},
title = {Pairing-Based Onion Routing with Improved Forward Secrecy},
howpublished = {Cryptology ePrint Archive, Report 2008/080},
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.