@misc{cryptoeprint:2010:337,
author = {Vincent Rijmen},
title = {Practical-Titled Attack on AES-128 Using Chosen-Text Relations},
howpublished = {Cryptology ePrint Archive, Report 2010/337},
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.