On Wed, May 26, 2021 at 05:11:24PM -0700, Andres Freund wrote:
> Hi,
>
> On 2021-05-25 17:12:05 -0400, Bruce Momjian wrote:
> > If we used a block cipher instead of a streaming one (CTR), this might
> > not work because the earlier blocks can be based in the output of
> > later blocks.
>
> What made us choose CTR for WAL & data file encryption? I checked the
> README in the patchset and the wiki page, and neither seem to discuss
> that.
>
> The dangers around nonce reuse, the space overhead of storing the nonce,
> the fact that single bit changes in the encrypted data don't propagate
> seem not great? Why aren't we using something like XTS? It has obvious
> issues as wel, but CTR's weaknesses seem at least as great. And if we
> want a MAC, then we don't want CTR either.
We chose CTR because it was fast, and we could use the same method for
WAL, which needs a streaming, not block, cipher.
--
Bruce Momjian <bruce@momjian.us> https://momjian.us
EDB https://enterprisedb.com
If only the physical world exists, free will is an illusion.