@misc{cryptoeprint:2012:151,
author = {Alexander Rostovtsev and Alexey Mizyukin},
title = {On Boolean Ideals and Varieties with Application to Algebraic Attacks},
howpublished = {Cryptology ePrint Archive, Report 2012/151},
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.