Internal cache, the gallery and RAM are three different boundaries; deleting one copy does not prove that every copy is gone.
End-to-end encryption protects an image in transit; once it is opened, the security of the viewable copy also depends on the device and the app’s storage practices. But not every temporary file on Android is public, and not every cached image automatically enters the gallery.
To assess the risk, distinguish three locations instead of using the vague phrase “cache leak”: private app storage, shared storage such as the gallery, and active process memory or RAM. Each has different access rules and a different lifecycle.
Where can a decrypted image remain?
| Location | Typical use | Security consideration |
|---|---|---|
| Private internal app cache | Quickly displaying an image again | Other ordinary apps should not have unrestricted access to it |
| Gallery or shared storage | Saving, editing or sharing an image | It may be accessible to apps with permission and to backup services |
| RAM and display-component memory | Processing an image during use | Being temporary does not mean being protected from a compromised device |
| Exported copy or preview | Opening a file in another app | It may have an independent deletion lifecycle |
The Android storage documentation distinguishes app-specific storage from shared storage. The statement “every cache file is indexed by MediaStore” is therefore incorrect; the storage path, API used and permissions are decisive.
What protection does internal cache have?
Android isolates an app’s private internal storage from other ordinary apps. Official guidance recommends this storage for sensitive temporary data. A cache file may be deleted by the app or system before the app is uninstalled, but developers should not leave cleanup solely to a shortage of device storage. See the app-specific files guide.
This protection is not equivalent to “nobody can extract the file.” An attacker’s access to a locked phone, an unlocked phone, a vulnerable operating system or a rooted device is not the same. A valid forensic claim must specify the device model, system version, lock state and type of attacker access.
Why does keeping data in RAM not guarantee complete deletion?
Avoiding writing an unencrypted copy to disk can reduce the number of persistent copies. Clearing sensitive buffers may also be part of a defensive design. However, simply mentioning “RAM zeroing” does not justify declaring the probability of recovery to be zero.
During processing, an image may be copied into several buffers, libraries or display components. Clearing one buffer does not, by itself, prove that all copies have been deleted. Even if no persistent file is created, malware with access to the data while it is displayed may copy it. Encryption and memory management complement each other; neither replaces the other.
What can users do?
- Check gallery saving separately from automatic downloading. Receiving media for display inside the app is not necessarily the same as saving it to the gallery.
- Control photo backups. An exported image may enter cloud storage independently of the chat.
- Review other apps’ photo and file permissions. Do not confuse access needed for a particular task with ongoing access to the photo collection.
- Check with a test image. See which copy remains in the gallery or another app after receiving, opening, saving and deleting it.
- Check your recovery method before deleting app data. “Clear cache,” “clear storage” and signing out have different effects; the second may remove keys or necessary local data.
Testing with a non-sensitive image is useful, but the absence of a file in the gallery does not prove that no traces exist on the device.
How should developers test cleanup?
Testing should cover the entire media path: receipt, decryption, display, sharing, closing the screen, signing out and signing back in. Downloads or preview-generation operations already in progress must be coordinated with the sign-out policy; otherwise, a new file might be written after cleanup. This is a testable scenario, not a proven claim about every messenger.
Test a specific version and record file locations and the result of each step. Android security recommendations emphasize minimizing access and keeping sensitive data in an appropriate location.
What does this mean for Livara?
Livara’s threat model does not guarantee protection of a compromised or unlocked device. Documentation of encryption in transit alone is not evidence for the claim that “no unencrypted copy remains in cache.” Such a claim requires examination of a specific app version and its media paths.
Bottom line: Know the locations and number of image copies. Reducing extra copies, using a suitable device lock and updating are important; a promise of “zero recovery” without testing and a threat model is not a reliable criterion.
