Messages in this thread | | | Date | Fri, 23 Jun 2017 20:09:57 -0400 | From | Theodore Ts'o <> | Subject | Re: [PATCH v5] fscrypt: Add support for AES-128-CBC |
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On Mon, Jun 19, 2017 at 09:27:58AM +0200, David Gstir wrote: > From: Daniel Walter <dwalter@sigma-star.at> > > fscrypt provides facilities to use different encryption algorithms which > are selectable by userspace when setting the encryption policy. Currently, > only AES-256-XTS for file contents and AES-256-CBC-CTS for file names are > implemented. This is a clear case of kernel offers the mechanism and > userspace selects a policy. Similar to what dm-crypt and ecryptfs have. > > This patch adds support for using AES-128-CBC for file contents and > AES-128-CBC-CTS for file name encryption. To mitigate watermarking > attacks, IVs are generated using the ESSIV algorithm. While AES-CBC is > actually slightly less secure than AES-XTS from a security point of view, > there is more widespread hardware support. Using AES-CBC gives us the > acceptable performance while still providing a moderate level of security > for persistent storage. > > Especially low-powered embedded devices with crypto accelerators such as > CAAM or CESA often only support AES-CBC. Since using AES-CBC over AES-XTS > is basically thought of a last resort, we use AES-128-CBC over AES-256-CBC > since it has less encryption rounds and yields noticeable better > performance starting from a file size of just a few kB. > > Signed-off-by: Daniel Walter <dwalter@sigma-star.at> > [david@sigma-star.at: addressed review comments] > Signed-off-by: David Gstir <david@sigma-star.at> > Reviewed-by: Eric Biggers <ebiggers@google.com>
Thanks, applied.
- Ted
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