@misc{cryptoeprint:2015:183,
author = {Céline Blondeau and Kaisa Nyberg},
title = {New Links Between Differential and Linear Cryptanalysis},
howpublished = {Cryptology ePrint Archive, Report 2015/183},
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.