Retrieve a sha256 from another sha256

Question

I have a project where we are supposed to find a sha256 from another sha256.

For example we have

hash1 = "45f1bc22c29626c6db37d483273afbe0f6c434de02fe86229d50c9e71ed144fc"

and we would have to find

hash0 = "5495a885b7f445a198cc5b67a517a0e0536792ab3e7ead18a12c75f8310a9b89"

hash1 is just the hash0 used in a sha256 function.

Initially, I went on to redo every possibility of sha256 but it may do a lot and take a lot of time. If you have any idea how I could do this, even see if it's possible?

Answer 1

It's impossible, hashes can't be inverted, regardless if they're hashes of hashes or of other content. You could try all the combinations, sure, knowing that the source is a 256-bit sequence, but this is practically prohibitive, although there's always a possibility of 1 out of 2^256 that you guess it at the first try:-)