@misc{cryptoeprint:2012:550,
author = {David Cash and Alptekin Kupcu and Daniel Wichs},
title = {Dynamic Proofs of Retrievability via Oblivious RAM},
howpublished = {Cryptology ePrint Archive, Report 2012/550},
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.