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

On Wed, Jul 10, 2019 at 02:44:30PM -0400, Stephen Frost wrote:
> Greetings,
> 
> * Bruce Momjian (bruce@momjian.us) wrote:
> > On Wed, Jul 10, 2019 at 12:38:02PM -0600, Ryan Lambert wrote:
> > > 
> > >     what is it that gets stored in the page for
> > >     decryption use, the nonce or the IV derived from it?
> > > 
> > > 
> > > I believe storing the IV is preferable and still secure per [1]: "The IV need
> > > not be secret"
> > > 
> > > Beyond needing the database oid, if every decrypt function has to regenerate
> > > the IV from the nonce that will affect performance.  I don't know how expensive
> > > the forward hash is but it won't be free.
> > 
> > Well, I think we have three options.  We have 3 4-byte integers
> > (pg_class.oid, LSN, page-number) that could be concatenated to be the
> > IV, we could run those through a hash, or we could run them through the
> > encryption function with the secret.
> 
> I didn't see where it was said that using a hash was a good idea in this
> context..?  Encrypting it with the key looked like it was discussed as a

I didn't either, except it was referenced above as "forward hash".  I
don't know why that was suggested, which is why I listed it as an
option/suggestion.

> viable option.  I had understood that part of the point of using the

Agreed.

> table OID and page-number was also so that we didn't have to explicitly
> store the result, therefore requiring us to need less space on the page
> to make this happen.

Yep!

-- 
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
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