@misc{cryptoeprint:2010:242,
author = {Yang ZHANG and Jun-Liang CHEN},
title = {Efficient Access Control of Sensitive Data Service in Outsourcing Scenarios},
howpublished = {Cryptology ePrint Archive, Report 2010/242},
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.