@misc{cryptoeprint:2015:208,
author = {Ioana Boureanu, Aikaterini Mitrokotsa and Serge Vaudenay},
title = {Towards Secure Distance Bounding},
howpublished = {Cryptology ePrint Archive, Report 2015/208},
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.