Next up in the series of PCTF writeups, is problem #6, a .NET challenge. Unfortunately, the .Net Reflector recently went pay, although its only $35, and comes with a 2 week trial. We'll go with the trial.
Great. Its obfuscated, but we kind of expected that, and we know we're looking for a valid key.
Before we get too far, this is what the application is looking for, so we're looking for 3 values ranging from 0->255 that fit and will activate our controller.
We now know that they take 5 values from the sliders: h = first bar, j = second bar, and i = third bar. From that, we get num = first bar, num2 = second bar, num3 = third bar, num4 = second bar * third bar, and num5 = first bar * 3.
Time for some maths, we end up with the equality (replacing x, y, and z with the bars):
Now, we can't easily solve this, but we've got some fairly limited bounds, 256 > x > 77, 255 >= y >= 0, and 255 >= z >=0. So, only 12 million possibilities, give or take. GOGOGO scripting:
And that's all folks. Yes, that's ruby, and yes, that was plenty fast enough.