Comment by kaba0

In cryptography creating a one-way function is not a problem. The only thing required for that is loosing information, which is trivial. For example taking the first n bytes of a file is a one-way hash function (for most files). So reversing the hashes is most definitely not a problem.

Creating collisions could be though, eg. brute forcing a normal picture by modifying random pixels by a bit into matching an illegal content’s hash is a possibility.