ApoorvCTF 4.0 - GEM (Glen's Enigmatic Module)

You get two images (original and processed) and a script that recovers the 3x3 convolution kernel used on each RGB channel via least-squares. Running the script on these two images as args gives you three matrices:

Red:   [[ 1 -1  0], [-1  5 -1], [ 2 -1  0]]
Green: [[ 1  2  1], [-1  8 -1], [-3 -1  1]]
Blue:  [[-1 -4  1], [ 1  4  4], [-1  3  1]]

Flag format is apoorvctf{d1_d2_d3} where d1, d2, d3 are scalars from each matrix. The operation is the determinant.

det(Red)   = 1
det(Green) = 40
det(Blue)  = 35

The flag -

apoorvctf{1_40_35}

(You do NOT need a ./solve.py for this one. It’s just two commands. I’m not joking.)