Day 06: Twelve steps of Christmas

Description

On the sixth day of Christmas my true love sent to me…

six valid QRs,
five potential scrambles,
four orientation bottom and right,
and the rest has been said previously.

Solution

This is cool, I love Rubik’s cubes! Unfortunately I don’t have a printer, so we are going to solve this in-silico :)

We cut out all the squares with GIMP, and use python to generate all possible combinations of QR-quarters, and find the flag

  
from PIL import Image
from pyzbar.pyzbar import decode
import glob, itertools

def concat_h(im1, im2):
    dst = Image.new('RGB', (im1.width + im2.width, im1.height))
    dst.paste(im1, (0, 0))
    dst.paste(im2, (im1.width, 0))
    return dst

def concat_v(im1, im2):
    dst = Image.new('RGB', (im1.width, im1.height + im2.height))
    dst.paste(im1, (0, 0))
    dst.paste(im2, (0, im1.height))
    return dst


# load image parts
qrblocks = [Image.open(a) for a in glob.glob("dec6-qrcodes/good_tr/*.png")]
qrbr = [Image.open(a) for a in glob.glob("dec6-qrcodes/br/*.png")]
perm = itertools.permutations(qrblocks,3)

found = 0
for i in perm:
  tl = i[0].rotate(90)
  tr = i[1]
  bl = i[2].rotate(180)
  for br in qrbr:
    top = concat_h(tl,tr)
    bottom = concat_h(bl,br)
    final = concat_v(top,bottom)
    dec = decode(final)
    if dec != []:
      print(dec[0].data)
      final.save("dec6_qrcode"+str(found)+".png")
      found+=1

This gives the following output:

b'HV20{Erno_                                                      '
b'_be_proud.                                                      '
b'Rubik_would                                                     '
b'#HV20QRubicsChal}                                               '
b'_Valid.                                                         '
b'Petrus_is                                                       '

whoo! we found all the fragments! Now its just a matter of putting them in the right order and we have our flag :)

These were the qr images