@misc{cryptoeprint:2012:349,
author = {Subhadeep Banik and Subhamoy Maitra and Santanu Sarkar},
title = {A Differential Fault Attack on Grain-128a using MACs},
howpublished = {Cryptology ePrint Archive, Report 2012/349},
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.