It's moderately expensive even with MD5. Ideally you'd like to use the same prefix and use the collision itself to choose between the two. This is easy with cod

It's moderately expensive even with MD5. Ideally you'd like to use the same prefix and use the collision itself to choose between the two. This is easy with code, trickier with images, and even trickier with text-based PDFs but still possible: https://www.makomk.com/~aidan/selfmd5-lastfix.pdf https://www.makomk.com/~aidan/selfmd5-lastfix.pdf