CTF: VolgaCTF VC task

27/03/17 — capitol

bits

name:

VC

category:

crypto

points:

50

Writeup

We were given two images, both containing black and white noise. A B

Since it’s a crypto challege with low points, we guessed that it’s a simple XOR.

The quickest way to xor two images is with a command line one liner:

convert A.png B.png -fx "(((255*u)&(255*(1-v)))|((255*(1-u))&(255*v)))/255" C.png

That produced this result: C

Flag: VolgaCTF{Classic_secret_sharing_scheme}