If you are going to the trouble of layering encryption like that you may as well using a MAC with similar construction. It is poorly thought out. I would also b

If you are going to the trouble of layering encryption like that you may as well using a MAC with similar construction. It is poorly thought out. I would also be much more worried about scrypt than AES in the future, it has had much less review yet is not layered in the same way. Also the go reference implementation is not idiomatic, It does not conform to the interface of other encryption functions in the standard library. EDIT: I was wrong, they do double up on MAC's but do not on the KDF.