@misc{cryptoeprint:2010:285,
author = {Pawel Morawiecki and Marian Srebrny},
title = {A SAT-based preimage analysis of reduced KECCAK hash functions },
howpublished = {Cryptology ePrint Archive, Report 2010/285},
year = {2010},
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.