@misc{cryptoeprint:2012:247,
author = {Xusheng Zhang and Kunpeng Wang and Dongdai Lin},
title = {On Efficient Pairings on Elliptic Curves over Extension Fields},
howpublished = {Cryptology ePrint Archive, Report 2012/247},
year = {2012},
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.