@misc{cryptoeprint:2014:931,
author = {Thomas Peyrin and Siang Meng Sim and Lei Wang and Guoyan Zhang},
title = {Cryptanalysis of JAMBU},
howpublished = {Cryptology ePrint Archive, Report 2014/931},
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.