On Fri, Oct 04, 2019 at 06:06:10PM -0400, Bruce Momjian wrote:
On Fri, Oct 4, 2019 at 11:48:19PM +0200, Tomas Vondra wrote:
On Fri, Oct 04, 2019 at 04:58:14PM -0400, Bruce Momjian wrote:
> On Fri, Oct 4, 2019 at 10:46:57PM +0200, Tomas Vondra wrote:
> > Oracle also has a handy "TDE best practices" document [2], which says
> > when to use column-level encryption - let me quote a couple of points:
> >
> > * Location of sensitive information is known
> >
> > * Less than 5% of all application columns are encryption candidates
> >
> > * Encryption candidates are not foreign-key columns
> >
> > * Indexes over encryption candidates are normal B-tree indexes (this
> > also means no support for indexes on expressions, and likely partial
> > indexes)
> >
> > * No support from hardware crypto acceleration.
>
> Aren't all modern systems going to have hardware crypto acceleration,
> i.e., AES-NI CPU extensions. Does that mean there is no value of
> partial encryption on such systems? Looking at the overhead numbers I
> have seen for AES-NI-enabled systems, I believe it.
>
That's a good question, I don't know the answer. You're right most
systems have CPUs with AES-NI these days, and I'm not sure why the
column encryption does not leverage that.
Maybe it's because column encryption has to encrypt/decrypt much smaller
chunks of data, and AES-NI is not efficient for that? I don't know.
For full-cluster TDE with AES-NI-enabled, the performance impact is
usually ~4%, so doing anything more granular doesn't seem useful. See
this PGCon presentation with charts:
https://www.youtube.com/watch?v=TXKoo2SNMzk#t=27m50s
Having anthing more fine-grained that all-cluster didn't seem worth it.
Using per-user keys is useful, but also much harder to implement.
Not sure I follow. I thought you are asking why Oracle apparently does
not leverage AES-NI for column-level encryption (at least according to
the document I linked)? And I don't know why that's the case.
FWIW performance is just one (supposed) benefit of column encryption,
even if all-cluster encryption is just as fast, there might be other
reasons to support it.
regards
--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
