Connecting an OpenEdge 12.x client, such as OpenEdge 12.x studio or editor, to an OpenEdge 11.x database with DBAUTHKEY fails with the following error: 

Connection to database from a previous release that contains a dbauthkey is not allowed. (19397).

An upgrade to the cryptographic technologies used by the OpenEdge version 12 DBAUTHKEY/RCODEKEY feature prevents the validation of the shared secret key between any combination of version 11 and version 12 databases and database clients.