Earlier quoted context omitted.
>not realistic The odds are zero. 1/2^256 = 0. In cryptography these odds are treated as zero until you generate close to 2^128 images. Unfortunately there's no word in natural English to describe how unlikely. The most precise is "zero".
You should spend some time with an internet search engine and the term "perceptual hashing". What you're talking about is another type of hashing, which can be useful for classifying image files , but not images . The former has a very concrete definition that is specified down to the bit; the latter is a fuzzy space because it's trying to yield similar (not necessarily identical) hashes for images that humans consid…
Yeah that's bad. What about deepdream/CNN reversing? Couldn't a rogue apple engineer just create a innocuous looking false positive, say a cat picture, share it on Reddit, and everybody who downloads it is flagged to police for CSAM?