@misc{cryptoeprint:2010:441,
author = {Matthieu Rivain and Emmanuel Prouff},
title = {Provably Secure Higher-Order Masking of AES},
howpublished = {Cryptology ePrint Archive, Report 2010/441},
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.