Re: XTS cipher mode for cluster file encryption

On Sat, Oct 16, 2021 at 09:15:05AM -0700, Andres Freund wrote:
> Hi,
> 
> On 2021-10-16 10:16:25 -0400, Bruce Momjian wrote:
> > As a final comment to Andres's email, adding a GCM has the problems
> > above, plus it wouldn't detect changes to pg_xact, fsm, vm, etc, which
> > could also affect the integrity of the data.  Someone could also restore
> > and old copy of a patch to revert a change, and that would not be
> > detected even by GCM.
> 
> > I consider this a checkbox feature and making it too complex will cause
> > it to be rightly rejected.
> 
> You're just deferring / hiding the complexity. For one, we'll need integrity
> before long if we add encryption support. Then we'll deal with a more complex
> on-disk format because there will be two different ways of encrypting. For
> another, you're spreading out the security analysis to a lot of places in the
> code and more importantly to future changes affecting on-disk data.
> 
> If it's really just a checkbox feature without a real use case, then we should
> just reject requests for it and use our energy for useful things.

Agreed.  That is the conclusion I came to in May:

	https://www.postgresql.org/message-id/20210526210201.GZ3048%40momjian.us
	https://www.postgresql.org/message-id/20210527160003.GF5646%40momjian.us

-- 
  Bruce Momjian          https://momjian.us
  EDB                                      https://enterprisedb.com

  If only the physical world exists, free will is an illusion.