From: | Bruce Momjian <bruce(at)momjian(dot)us> |
---|---|
To: | Stephen Frost <sfrost(at)snowman(dot)net> |
Cc: | Ants Aasma <ants(at)cybertec(dot)at>, Sasasu <i(at)sasa(dot)su>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
Subject: | Re: storing an explicit nonce |
Date: | 2021-10-07 19:11:26 |
Message-ID: | 20211007191126.GC24305@momjian.us |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
On Thu, Oct 7, 2021 at 02:52:07PM -0400, Stephen Frost wrote:
> > > Is there a particular reason why you would prefer not to use LSN? I suggested
> > > it because in my view having a variable tweak is still better than not having
> > > it even if we deem the risks of XTS tweak reuse not important for our use case.
> > > The comment was made under the assumption that requiring wal_log_hints for
> > > encryption is acceptable.
> >
> > Well, using the LSN means we have to store the LSN unencrypted, and that
> > means we have to carve out a 16-byte block on the page that is not
> > encrypted.
>
> With XTS this isn't actually the case though, is it..? Part of the
> point of XTS is that the last block doesn't have to be a full 16 bytes.
> What you're saying is true for XEX, but that's also why XEX isn't used
> for FDE in a lot of cases, because disk sectors aren't typically
> divisible by 16.
Oh, I was not aware of that XTS feature. Nice.
> https://en.wikipedia.org/wiki/Disk_encryption_theory
>
> Assuming that's correct, and I don't see any reason to doubt it, then
> perhaps it would make sense to have the LSN be unencrypted and include
> it in the tweak as that would limit the risk from re-use of the same
> tweak over time.
Yes, seems like a plan.
--
Bruce Momjian <bruce(at)momjian(dot)us> https://momjian.us
EDB https://enterprisedb.com
If only the physical world exists, free will is an illusion.
From | Date | Subject | |
---|---|---|---|
Next Message | Bruce Momjian | 2021-10-07 19:11:42 | Re: storing an explicit nonce |
Previous Message | Tom Lane | 2021-10-07 19:02:40 | Re: pgsql: Adjust configure to insist on Perl version >= 5.8.3. |