@misc{cryptoeprint:2012:083,
author = {Casey Devet and Ian Goldberg and Nadia Heninger},
title = {Optimally Robust Private Information Retrieval},
howpublished = {Cryptology ePrint Archive, Report 2012/083},
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.