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 --
