@misc{cryptoeprint:2011:304,
author = {Jia XU},
title = {Auditing the Auditor: Secure Delegation of Auditing Operation over Cloud Storage},
howpublished = {Cryptology ePrint Archive, Report 2011/304},
year = {2011},
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.