On Wed, Jun 20, 2018 at 06:19:40PM -0400, Joe Conway wrote:
> On 06/20/2018 05:12 PM, Bruce Momjian wrote:
> > On Mon, Jun 18, 2018 at 11:06:20AM -0400, Joe Conway wrote:
> > Even if they are encrypted with the same key, they use different
> > initialization vectors that are stored inside the encrypted payload, so
> > you really can't identify much except the length, as Robert stated.
Definitely use different IVs, and don't reuse them (or use cipher modes
where IV reuse is not fatal).
> The more you encrypt with a single key, the more fuel you give to the
> person trying to solve for the key with cryptanalysis.
With modern 128-bit block ciphers in modern cipher modes you'd have to
encrypt enough data to make this not a problem. On the other hand,
you'll still have other reasons to do key rotation. Key rotation
ultimately means re-encrypting everything. Getting all of this right is
very difficult.
So again, what's the threat model? Because if it's sysadmins/DBAs
you're afraid of, there are better things to do.
Nico
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