NullKey 
Importing usually makes another copy
Adding a document to a vault is different from moving it. Confirm whether your app retains the original, deletes it, or sends it to trash. Check each source app separately; a gallery and a document provider may handle deletion differently.
Verify more than the thumbnail
For photos, check orientation and detail. For documents that NullKey cannot display, a readable export can help you check the contents, but that export is outside the vault’s protection. A thumbnail alone does not show that the whole original was preserved.
Give yourself a way back
Make an encrypted backup and keep its unlocking secret available before removing your original. A recovery key alone cannot recreate deleted data. If a source is synced, understand whether a deletion will propagate to other devices or cloud storage. A recovery key opens data but does not preserve it; see how the key and backup work together. For private photos, read the Android photo guide and the photo vault workflow.
Deletion is not secure erasure
Trash, backups and other apps can retain copies. Optional original removal is off by default in NullKey. It verifies eligible local copies first. Supported photos and videos need Android’s confirmation to move to trash; other supported documents can be deleted permanently. Cloud and other-app sources are kept. Deletion is not guaranteed secure erasure.
