@misc{cryptoeprint:2015:797,
author = {Carmit Hazay and Muthuramakrishnan Venkitasubramaniam},
title = {What Security can we Achieve in 4-Rounds?},
howpublished = {Cryptology ePrint Archive, Report 2015/797},
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.