於 四，2013-09-26 於 02:27 +0200，Pavel Machek 提到：

On Wed 2013-09-25 15:16:54, James Bottomley wrote:

quoted

On Wed, 2013-09-25 at 17:25 -0400, Alan Stern wrote:

quoted

On Wed, 25 Sep 2013, David Howells wrote:

quoted

I have pushed some keyrings patches that will likely affect this to:

	http://git.kernel.org/cgit/linux/kernel/git/dhowells/linux-fs.git/log/?h=keys-devel

I intend to ask James to pull these into his next branch.  If he's happy to do
so, I can look at pulling at least your asymmetric keys patch on top of them.

This suggests a point that I raised at the Linux Plumbers conference:

Why are asymmetric keys used for verifying the hibernation image?  It
seems that a symmetric key would work just as well.  And it would be a
lot quicker to generate, because it wouldn't need any high-precision
integer computations.

The reason is the desire to validate that the previous kernel created
something which it passed on to the current kernel (in this case, the
hibernation image) untampered with.  To do that, something must be
passed to the prior kernel that can be validated but *not* recreated by
the current kernel.

I don't get this. Why is it important that current kernel can't
recreate the signature?

Current kernel is not considered malicious (if it were, you have worse
problems).

Current boot kernel should not malicious especially when UEFI secure
boot enabled.

								Pavel

PS: And yes, it would be nice to have
Documentation/power/swsusp-uefi.txt (or something) explaining the
design.

Thanks for your suggestion, I will write the swsusp-uefi.txt to
explaining the design in next version.


Thanks a lot!
Joey Lee