@misc{cryptoeprint:2012:705,
author = {Nir Bitansky and Sanjam Garg and Daniel Wichs},
title = {Why "Fiat-Shamir for Proofs" Lacks a Proof},
howpublished = {Cryptology ePrint Archive, Report 2012/705},
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.