@misc{cryptoeprint:2010:144,
author = {David Cash and Matthew Green and Susan Hohenberger},
title = {New Definitions and Separations for Circular Security},
howpublished = {Cryptology ePrint Archive, Report 2010/144},
year = {2010},
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.