you are apparently using some cool/sophisticated checks in secret_solver to avoid hacking attempts, but in my opinion it might be safer to just leave the checking of whether the solution is correct or not to your .p function itself, instead of having your .p function return the correct value (e.g. something like testsuite in http://www.mathworks.com/matlabcentral/cody/problems/1969-self-description)

The code is actually doing what it says it is doing, nothing fancy in there. But you are right, for the next one I will take the approach in [Alfnie1969]. Thanks!

Next one is out! http://www.mathworks.com/matlabcentral/cody/problems/2449-back-to-the-future-ii