Retrieve original image after crop (cut)

Question

I am doing a small program about using an image to calculate the Message digest, but what i also need to do is i need to put the another image into this original image, and put this modified image (original image embed by another image) to cloud. There is my question that if i tried to download this modified image from cloud, and any way i can remove image which was embeded into original image, and using this original image to calculate to get Message digest the same as the original Message digest???

There are two ways i was trying to do, and i drew it through paper(maybe easy to understand what i am trying to say) below

Method 1

Method 2