To keep a concise title I have left out a few details, but here is the dilemma:
I have a cops post that has not yet been cracked. I would like to reward the first person to figure out my solution but there are very few combinations to be checked and it is almost certain that the first person to crack it will do so by brute force. In order to not reward the person with the best computer I would like to give a substantial bounty to the first person to provide me a proof that their crack indeed works. (Even with the answer at hand this is not an easy task) However if they are not the first person to crack the submission they cannot make an answer on the robber's thread for me to reward. In the end I don't really care how the robber got the answer as long as I know that they understand how it works.
One thought I had was that I might be able to mark my answer safe and reveal the program (if the period expires without it being cracked) and reverse its safe status when presented with a proof (via chat or comments) so that the robber could "crack" it. But this might not be considered fair by the community.
Is there any good way for me solve this dilemma?