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  The challenge: Category : Malware Reverse Engineering Level : easy   Points : 50 The correct input is the flag,format flag{xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} Challenge Link : https://s3-eu-west-1.amazonaws.com/hubchallenges/Reverse/GUI.exe The solution :  I open the GUI.exe using dnspy tool because it is a .net file  it contains form with 8 check boxes and button and 4 labels when you hit the button the label will change to number  when i take a look at the button click event i saw this the code is very simple  every time the button clicked it takes the number 2 raised to the power num2 num2 is the index of the checkbox that we checked it from array  then calculate the result and store it in num  so we Jumped into conclusion : checkbox1.checked = array(0) >> num = math.pow(2,0) = 1 checkbox2.checked = array(1) >> num = math.pow(2,1) = 2 checkbox3.checked = array(2) >> num = math.pow(2,2) = 4 checkbox4.checked = array(3) >&g