/blog
Cracking the MI5 puzzle.
Cleaning up hard-drive; found some old code.
MI5 put this puzzle on their website. (It’s still there - just scroll down):
The puzzle screams encoded message, because that’s not a picture of anything. I thought that perhaps this might be a ruse, and that something a bit more sophisticated is being used here, e.g. steganography.
Looking at the bitmap data showed clean numbers, i.e. only 2 colours were used, not slightly different shades of two colours (which would hint at stego).
I went back to the first idea, and lo and behold - it’s a recruitment drive!
python main.py
b’Congratulations, you solved the puzzle! Why don\x92t you apply to join our team? mi5.gov.uk/careers ‘
Bit underwhelming. I fully expected a chopper to land outside in the garden the moment my Python script finished running. A lady clad in black would kick my door down, run over to me, and say in a forceful yet husky voice “The Queen needs you.”
Spoiler: Here’s the code, but please do try it yourself and experience your own Bond moment (yes, I know he’s MI6…):
main.py
from PIL import Image, ImageFont, ImageDraw
import numpy as np
# these values gleaned by looking at the bitmap.
def bi(tup):
if tup[0] == 58:
return 1
elif tup[0] == 232:
return 0
else:
return -1
def ribbon(file_location="puzzle.png"):
encoded_image = Image.open(file_location)
im = np.asarray(encoded_image, dtype=np.uint8)
binarised = [bi(im[i,j]) for i,j in np.ndindex(im.shape[:2])]
next = binarised[0]
count = 0
results = []
for i in binarised:
if next == i:
count = count + 1
else:
results.append(count)
count = 1
next = i
results.append(count)
strung = [(chr(i)) for i in results]
hex = ''.join(strung)
hex = hex.replace('-', '')
decoded = bytes.fromhex(hex)
print(decoded)
if __name__ == "__main__":
ribbon()
Pipfile
[[source]]
name = "pypi"
url = "https://pypi.org/simple"
verify_ssl = true
[dev-packages]
[packages]
Pillow = "*"
numpy = "*"
[requires]
python_version = "3.7"