@misc{cryptoeprint:2015:938,
author = {Dong Pyo Chi and Jeong Woon Choi and Jeong San Kim and Taewan Kim},
title = {Lattice Based Cryptography for Beginners},
howpublished = {Cryptology ePrint Archive, Report 2015/938},
year = {2015},
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.