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

On Mon, Jun 18, 2018 at 09:49:20AM -0400, Robert Haas wrote:
> figure stuff out.  You can infer something about the length of
> particular values.  Perhaps you can find cases where the same
> encrypted value appears multiple times.  If there's a btree index, you

Most encryption methods use a random initialization vector (IV) for each
encryption, e.g. pgp_sym_encrypt(), but length might allow this, as you
stated.

> know the ordering of the values under whatever ordering semantics
> apply to that index.  It's unclear to me how useful such information

I don't think an ordered index is possible, only indexing of encrypted
hashes, i.e. see this and the next slide:

    https://momjian.us/main/writings/crypto_hw_use.pdf#page=86

> would be in practice or to what extent it might allow you to attack
> the underlying cryptography, but it seems like there might be cases
> where the information leakage is significant.  For example, suppose
> you're trying to determine which partially-encrypted record is that of
> Aaron Aardvark... or this guy:
> https://en.wikipedia.org/wiki/Hubert_Blaine_Wolfeschlegelsteinhausenbergerdorff,_Sr.
> 
> Recently, it was suggested to me that a use case for column-level
> encryption might be to prevent casual DBA snooping.  So, you'd want
> the data to appear in pg_dump output encrypted, because the DBA might
> otherwise look at it, but you wouldn't really be concerned about the
> threat of the DBA loading a hostile C module that would steal user
> keys and use them to decrypt all the data, because they don't care
> that much and would be fired if they were caught doing it.

Yes, that is a benefit that is not possible with page-level encryption. 
It also encrypts the WAL and backups automatically;  see:

    http://momjian.us/main/writings/crypto_hw_use.pdf#page=97

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

+ As you are, so once was I.  As I am, so you will be. +
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