Re: [Proposal] Table-level Transparent Data Encryption (TDE) and Key Management Service (KMS)

On Sun, Jun 16, 2019 at 07:07:20AM -0400, Joe Conway wrote:
> On 6/15/19 9:28 PM, Bruce Momjian wrote:
> >> There are reasons other than performance to want more granular than
> >> entire cluster encryption. Limiting the volume of encrypted data with
> >> any one key for example. And not encrypting #1 & 2 above would help
> >> avoid known-plaintext attacks I would think.
> >
> > There are no known non-exhaustive plaintext attacks on AES:
> >
> > https://crypto.stackexchange.com/questions/1512/why-is-aes-resistant-to-known-plaintext-attacks
>
> Even that non-authoritative stackexchange thread has varying opinions.
> Surely you don't claim that limiting know plaintext as much as is
> practical is a bad idea in general.

I think we have to look at complexity vs. benefit.

> > Even if we don't encrypt the first part of the WAL record (1 & 2), the
> > block data (3) probably has enough format for a plaintext attack.
>
> Perhaps.
>
> In any case it doesn't address my first point, which is limiting the
> volume encrypted with the same key. Another valid reason is you might
> have data at varying sensitivity levels and prefer different keys be
> used for each level.

That seems quite complex.

> And although I'm not proposing this for the first implementation, yet
> another reason is I might want to additionally control "transparent
> access" to data based on who is logged in. That could be done by
> layering an additional key on top of the per-tablespace key for example.
>
> The bottom line in my mind is encrypting the entire database with a
> single key is not much different/better than using filesystem
> encryption, so I'm not sure it is worth the effort and complexity to get
> that capability. I think having the ability to encrypt at the tablespace
> level adds a lot of capability for minimal extra complexity.

I disagree.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ As you are, so once was I. As I am, so you will be. +
+ Ancient Roman grave inscription +