@misc{cryptoeprint:2010:658,
author = {Uri Avraham and Eli Biham and Orr Dunkelman},
title = {ABC - A New Framework for Block Ciphers},
howpublished = {Cryptology ePrint Archive, Report 2010/658},
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.