@misc{cryptoeprint:2012:090,
author = {Adeline Langlois and Damien Stehle},
title = {Worst-Case to Average-Case Reductions for Module Lattices},
howpublished = {Cryptology ePrint Archive, Report 2012/090},
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.