In order to confirm that the Encryption key that you have on file is indeed the correct one, you can test this out. You can follow the steps here:
- Ensure you are running at least 8.5.20, otherwise download the latest version from here.
- Navigate to [Setup] > [Backup Settings] > [Master Encryption Key]. Click on [Test Master Encryption Key]
Then you will be prompted to enter your current master encryption key and then simply click on [Test Key] in order to validate it:
If your Master Encryption Key is not validated it means that the wrong one is being inputted. There is no method of recovery for the old key in order to ensure the highest security for your backups. At this point, it is suggested to click [Click here to change it] and that will start a fresh backup set with the new key.