@misc{cryptoeprint:2013:838,
author = {Shi Bai and Steven D. Galbraith},
title = {An improved compression technique for signatures based on learning with errors},
howpublished = {Cryptology ePrint Archive, Report 2013/838},
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.