Acquiring Hidden Space via Modifying Block Bitmap for Android Devices
Mobile devices are widely used to process sensitive data. In certain situations, the sensitive data must be hidden rather than be encrypted. The existing approaches of setting up hidden space are not suitable for advanced Ext4 file system because they may require external storage device. To address the issue, we propose a novel method to establish the hidden space in Ext4 via artificially modifying the block bitmaps. To further improve usefulness of our method, we modify the multiply bits of the block bitmaps one time by creating a “host file” rather than by bit. This method is lightweight and does not require modifying the linux kernel and has no effect on the normal operations of the operating system. To validate the method performance, distributions of hidden spaces under different storage capacity are conducted. The results show that our method is effective and reliable.
KeywordsHidden space Ext4 Block bitmap
This work was supported in part by the key scientific research program of He’nan Education Department of China (No. 61361166006).
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