@misc{cryptoeprint:2013:293,
author = {Vadim Lyubashevsky and Chris Peikert and Oded Regev},
title = {A Toolkit for Ring-LWE Cryptography},
howpublished = {Cryptology ePrint Archive, Report 2013/293},
year = {2013},
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.