A visual approach to interpreting NAND flash memory

The research described in this paper proposes methods for visually interpreting the content of raw NAND flash memory images into higher level visual artefacts of assistance in reverse engineering and interpreting flash storage formats. A novel method of reverse engineering the structure and layout of individual memory locations within NAND flash images, based on injecting a known signal into a test NAND environment is also proposed. Omissions in the current theory of operation of flash, in particular the role of flash memory controllers in transforming the raw NAND are identified, clarifying the cause of variations seen between images taken using pseudo physical and raw physical techniques. The effectiveness of the approach is validated against raw NAND images from YAFFS2 based Android phones, taken via JTAG and chip-off methods.