SiShredder

A secure file eraser for Android, inspired by Shreddit. Permanently destroys files by overwriting their contents with industry-standard sanitization patterns before deletion, so they can't be recovered with undelete tools.

For security and research use only. This project is provided strictly for lawful information-security, data-privacy, and research purposes. Data erasure is permanent and irreversible. The Software is provided with no warranty, and the author accepts no responsibility or liability for anything done with it: use is entirely at your own risk and your own legal responsibility. By using, building, or installing it you accept the full DISCLAIMER and the LICENSE. This is not legal advice.

Features File browser for shared storage with image/video thumbnails, folder navigation, and multi-select (tap files to select, tap folders to open, select-all in the top bar).

Shredding schemes (pick in Settings ⚙️):

Random (default): one pass of random data; correct on every kind of storage Zeros (fast): one pass of zeros; equivalent on encrypted internal storage Multi-pass standards (DoD, Gutmann, …) are deliberately not offered: on flash storage they add wear and time but no security. If a single overwrite lands in place the data is gone; if the storage remaps writes, every extra pass lands in the same wrong place. Use the free-space wipe for remapped-write filesystems.

How shredding works: each pass overwrites the file in place and fsyncs to disk; the file is then truncated to zero length, renamed to a random name (hiding the original name and size in directory metadata), and deleted. Folders are shredded recursively.

Free-space wipe: fills all unallocated space on internal shared storage with random data and releases it, destroying remnants of files deleted before the app was installed.

Confirmation dialogs, live progress with cancel, no background services, no network.

Permissions On Android 11+ the app asks for All files access (MANAGE_EXTERNAL_STORAGE) so it can shred arbitrary user files. It uses no other permissions and never touches the network.

Honest caveats On modern flash storage, wear-leveling and flash translation layers mean no overwrite-based tool (including the original Shreddit) can give a 100% physical guarantee that old data blocks are gone. Overwriting defeats ordinary recovery apps; for the strongest protection combine it with Android's built-in file-based encryption (enabled by default), so an attacker needs both the leftover blocks and your keys.

Two smaller limitations, shared with tools like GNU shred:

The rename-before-delete obscures the original filename best-effort, but filesystems don't scrub freed directory entries, so old name bytes can linger in directory blocks. File contents are unaffected. Copies made elsewhere (media-database thumbnails, app caches, cloud backups) are separate data that no shredder can reach.