@misc{cryptoeprint:2013:653,
author = {Florian Böhl and Gareth T. Davies and Dennis Hofheinz},
title = {RKA-KDM secure encryption from public-key encryption},
howpublished = {Cryptology ePrint Archive, Report 2013/653},
year = {2013},
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.