@misc{cryptoeprint:2010:613,
author = {Richard Lindner and Chris Peikert},
title = {Better Key Sizes (and Attacks) for LWE-Based Encryption},
howpublished = {Cryptology ePrint Archive, Report 2010/613},
year = {2010},
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.