@misc{cryptoeprint:2015:279,
author = {Jérémy Jean and Maria Naya-Plasencia and Thomas Peyrin},
title = {Improved Cryptanalysis of AES-like Permutations},
howpublished = {Cryptology ePrint Archive, Report 2015/279},
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.