Secure Data Destruction for Android is a tool to destroy files so they can not be recovered.
It will overwrites the actual content of those files, so a file recovery app may be able to restore these files but the content will be destroyed.
You should used it to destroy sensitive files before selling your device.
1. Wipe files: you select one or more files with the checkboxes and press the trash icon. The selected files will be overwritten. After the files are cleaned, they will be truncated, renamed and then deleted.
2. Wipe free space: long press the card in the list that you want to wipe. You can choose between the internal memory, an external microsd (FAT) or a USB key (FAT). After a confirmation, it will be filled with temporary files until the card is full to overwrite previously deleted files. These temporary files will be deleted at the end of the operation. It's not guaranteed that every free space will be overwritten, so some files could be recovered.
It could take a long time to wipe your data, so you should keep your device plugged during the operation.