Backups are a great idea, and encrypted backups are a even better idea. When backing up iOS devices on macOS, it is possible to set an encryption key to protect local files. There is however no straightforward GUI method to verify the encryption key.
conda create -n mvt python=3.10 conda activate mvt pip install mvt mvt-ios extract-key /path/to/backup
With the right password you will see
INFO [mvt.ios.decrypt] Derived decryption key for backup at path /path/to/backup is: "12345678901234567890"
CRITICAL [mvt.ios.decrypt] Failed to decrypt backup. Did you provide the correct password? Did you point to the right backup path?