The other day i thought about how great of encryption/decryption is handled within Oracle RDBMS with a wallet and encryption on a table level.
I do wonder, is this even a supported feature for OWM, for now i am guessing it isn't because of lifeless _LT tables that contain both live and history data.
I could also imagine a humongous hit on performance for all the IOs.
This isn't really a question, just a discussion.
It should work as expected. The encryption is done at the table level, so as long as it's been added prior to executing dbms_wm.EnableVersioning or you add it afterward using dbms_wm.AlterVersionedTable, it should work.
The performance hit(per row) and other considerations would be similar as compared to any other table using encryption.