# Depth of the SHA-256 collision search knowing partial input and final hashes

So I have a partial input data (string) PART1+UNKNOWN+PART2, length of UNKNOWN is self-describing. I have a bunch of valid hashes (about 8 or so) that are compatible.

My question is then: will bruteforce search for full collision given the data at hand be as long?

• Are you really asking for the collisions or finding the pre-images so that once can find the unknown part? – kelalaka Apr 6 at 16:58