@misc{cryptoeprint:2015:833,
author = {Mohammad Etemad and Alptekin Küpçü},
title = {Efficient Key Authentication Service for Secure End-to-end Communications},
howpublished = {Cryptology ePrint Archive, Report 2015/833},
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.