@misc{cryptoeprint:2015:070,
author = {Gaëtan Leurent and Lei Wang},
title = {The Sum Can Be Weaker Than Each Part},
howpublished = {Cryptology ePrint Archive, Report 2015/070},
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.