@misc{cryptoeprint:2012:126,
author = {Nuray At and Jean-Luc Beuchat and Ismail San},
title = {Compact Implementation of Threefish and Skein on FPGA},
howpublished = {Cryptology ePrint Archive, Report 2012/126},
year = {2012},
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.