Maybe try to have a look at it as permutations: the mapping "hex of the hash" → "its actual hash" is a (presumably random) permutation. And it's quite probable

Maybe try to have a look at it as permutations: the mapping "hex of the hash" → "its actual hash" is a (presumably random) permutation. And it's quite probable that such permutation has a fixed point: http://laurentmazare.github.io/2014/09/27/fixed-points-of-random-permutations http://laurentmazare.github.io/2014/09/27/fixed-points-of-ra... The problem is that we currently don't know how find it more efficiently than with exhaustive search, AFAIK. Edit: previously on HN: https://news.ycombinator.com/item?id=614079 https://news.ycombinator.com/item?id=614079