Robert Haas <robertmhaas@gmail.com> writes:
> On Mon, Jun 18, 2018 at 10:12 AM, Joe Conway <mail@joeconway.com> wrote:
>> Not necessarily. Our pages probably have enough predictable bytes to aid
>> cryptanalysis, compared to user data in a column which might not be very
>> predicable.
> Really? I would guess that the amount of entropy in a page is WAY
> higher than in an individual column value.
Depending on the specifics of the encryption scheme, having some amount
of known (or guessable) plaintext may allow breaking the cipher, even
if much of the plaintext is not known. This is cryptology 101, really.
At the same time, having to have a bunch of independently-decipherable
short field values is not real secure either, especially if they're known
to all be encrypted with the same key. But what you know or can guess
about the plaintext in such cases would be target-specific, rather than
an attack that could be built once and used against any PG database.
regards, tom lane