additionalData

extra data that can be used and can be validated together with the encrypted data.

It is optional and an empty array can be used, if no extra plaintext data needs to be validated.

For the purposes of backup, we can use a hash of the non-encrypted bytes of the file as additional data. This way, if these bytes were tempered with, the decryption will also fail. The idea is to do not trust any fruit from the poisoned tree.