NullKey 
Start with the copies you already have
A document can exist in your gallery, Downloads, a messaging app and a cloud backup at the same time. Moving one copy does not necessarily remove the others. Before choosing a vault, identify where the document came from and which apps may have copied or backed it up.
Choose the protection you actually need
A hidden album changes visibility. A separate locked folder adds an access boundary. An encrypted vault protects stored contents with encryption and a secret. These protections depend on the implementation and the state of your device. None makes an unlocked, compromised phone trustworthy.
Medical records, notes and everyday paperwork
People often keep letters from a clinic, test results, prescriptions, insurance details, tenancy papers and ID scans on the same phone as everything else. A private note suits the short facts: an allergy, a medication list, a policy number. A document suits the original file. In NullKey, photos and notes open inside the vault. PDFs, videos and other files stay encrypted, and you view them by exporting a readable copy, which leaves the vault’s protection. NullKey is not a medical record system and makes no claim about healthcare rules, so keep another copy of anything you cannot replace.
Keep recovery and backup separate
A recovery key helps unlock an existing vault. A backup preserves a copy of the data. To recover after a lost phone, you need a usable backup and the passphrase or recovery key that opens that backup. Store these separately from the phone.
A sensible routine
Start with sample files. Import copies, check their contents and make an encrypted backup. Restore into a separate, empty vault before removing any old app or original. NullKey stores photos, files and notes; PDFs and videos need a readable export to view in another app, outside the vault’s protection. For a photo-specific workflow, see our guide to private photos on Android; before removing any source copy, follow the copy-check steps. The NullKey photo vault explains what the app keeps protected.
