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

On Wed, Jul 31, 2019 at 3:29 PM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
>
>
> For WAL encryption,  before flushing WAL we encrypt whole 8k WAL page
> and then write only the encrypted data of the new WAL record using
> pg_pwrite() rather than write whole encrypted page. So each time we
> encrypt 8k WAL page we end up with encrypting different data with the
> same key+nonce but since we don't write to the disk other than space
> where we actually wrote WAL records it's not a problem. Is that right?

Hmm that's incorrect. We always write an entire 8k WAL page even if we
write a few WAl records into a page. It's bad because we encrypt
different pages with the same key+IV, but we cannot change IV for each
WAL writes as we end up with changing also
already-flushed-WAL-records. So we might need to change the WAL write
so that it write only WAL records we actually wrote.


Regards,

--
Masahiko Sawada
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center