A reverse patch for undoing a forward patch for obtaining a new binary image from an old binary image is generated in two parts. First a reverse index file is generated when the forward patch is created at a host or server. The reverse index file identifies regions of similarity between the old binary image and the new binary image. The reverse index file is transmitted with the forward patch to an electronic device. Second, while applying the forward patch to obtain the new binary image from the old binary image, the electronic device generates the reverse patch based upon the new binary image, the old binary image, and the reverse index file. The forward patch and reverse patch may both be incremental patches. Incremental patches are generated and applied on a sector-by-sector basis.