@misc{cryptoeprint:2014:1026,
author = {H. W. Lenstra, Jr. and A. Silverberg},
title = {Lattices with Symmetry},
howpublished = {Cryptology ePrint Archive, Report 2014/1026},
year = {2014},
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.