@misc{cryptoeprint:2015:091,
author = {Christoph Dobraunig and Maria Eichlseder and Florian Mendel},
title = {Related-Key Forgeries for Prøst-OTR},
howpublished = {Cryptology ePrint Archive, Report 2015/091},
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.