@misc{cryptoeprint:2010:576,
author = {Joppe W. Bos and Onur Ozen and Martijn Stam},
title = {Efficient Hashing using the AES Instruction Set},
howpublished = {Cryptology ePrint Archive, Report 2010/576},
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.