@misc{cryptoeprint:2013:536,
author = {Feng Zhang and Yanbin Pan and Gengran Hu},
title = {A Three-Level Sieve Algorithm for the Shortest Vector Problem},
howpublished = {Cryptology ePrint Archive, Report 2013/536},
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.