On Thu, Jul 25, 2019 at 09:11:18PM -0400, Sehrope Sarkuni wrote: > On Thu, Jul 25, 2019 at 8:50 PM Bruce Momjian <br...@momjian.us> wrote: > > On Thu, Jul 25, 2019 at 08:44:40PM -0400, Sehrope Sarkuni wrote: > > You can still use CTR mode and include those to make the key + IV unique > by > > adding them to the derived key rather than the IV. > > > > The IV per-page would still be LSN + page-number (with the block number > added > > as it's evaluated across the page) and the relfilenode, heap/index, > database, > > and anything else to make it unique can be included in the HKDF to > create > the > > per-file derived key. > > I thought if we didn't have to hash the stuff together we would be less > likely to get collisions with the IV. > > > IV creation not use any hashing and would never have collisions with the same > key as it's LSN + page + block (concatenation). > > The derived keys would also not have collisions as the HKDF prevents that. > Deriving two matching keys with different inputs has the same chance as > randomly generating matching HMACs (effectively nil with something like > HMAC-SHA-256). > > So there wouldn't be any reuse of the same key + IV. Even if two different > files are encrypted with the same LSN + page the total operation (key + IV) > would be different as they'd be using different derived keys.
Oh, mix the value into the derived key, not into the IV --- got it. -- Bruce Momjian <br...@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + As you are, so once was I. As I am, so you will be. + + Ancient Roman grave inscription +
