@misc{cryptoeprint:2015:372,
author = {Jeremy Jean and Ivica Nikolic and Thomas Peyrin and Lei Wang and Shuang Wu},
title = {Security Analysis of PRINCE},
howpublished = {Cryptology ePrint Archive, Report 2015/372},
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.