fixed format

create_qrcode.py

@@ -1,69 +0,0 @@
-import argparse
-from typing import List
-import qrcode
-from PIL import Image
-from pathlib import Path
-import random
-
-NUM_PIECES = 3
-TILE = 78
-
-def generate_qrcode(data: str) -> Image:
-    qr = qrcode.QRCode(version=25, box_size=2, error_correction=qrcode.ERROR_CORRECT_L, border=0)
-    qr.add_data(data)
-    return qr.make_image()
-
-
-def cut_pieces(image: Image) -> List[Image]:
-    pieces = []
-
-    for x, y in [(x, y) for x in range(NUM_PIECES) for y in range(NUM_PIECES)]:
-        pieces.append(image.crop((x * TILE, y * TILE, x * TILE + TILE, y * TILE + TILE)))
-
-    return pieces
-
-
-def scramble_qr_code(payloadList: List[Image], seed: str) -> Image:
-    height_piece, width_piece = payloadList[0].size
-    random.seed(seed)
-    scrambled_width = 3
-    random.shuffle(payloadList)
-
-    new_qr_code = Image.new("RGB", (width_piece * scrambled_width, height_piece * NUM_PIECES))
-    for x, y in [(x, y) for x in range(scrambled_width) for y in range(NUM_PIECES)]:
-        piece = payloadList[x + scrambled_width * y]
-        new_qr_code.paste(piece, (x * width_piece, y * height_piece))
-
-    return new_qr_code
-
-
-def generate_scrambled_qrcode(seed: str, output_dir: Path, name: str):
-    with open("./secret_message.txt", "r") as secret:
-        message = secret.read()
-     
-    qr_code = generate_qrcode(message + seed)
-    
-    qr_pieces = cut_pieces(qr_code)
-    scrambled_qr_code = scramble_qr_code(qr_pieces, seed)
-
-    output_dir.mkdir(parents=True, exist_ok=True)
-    scrambled_qr_code.save(output_dir / name)
-
-
-def main():
-    parser = argparse.ArgumentParser(description="Generates a scrambled QR code with optional decoy pieces.")
-    parser.add_argument("seed", type=str, help="The password to scramble the QR code.")
-    parser.add_argument("output_dir", type=Path, help="Directory where the output will be stored")
-    parser.add_argument("-o", "--output", type=str, default="secret_message.png", help="The name of the output image file.")
-    
-    args = parser.parse_args()
-
-    generate_scrambled_qrcode(
-        seed=args.seed, 
-        output_dir=args.output_dir,
-        name=args.output
-    )
-
-
-if __name__ == "__main__":
-    main()

description.yml

@@ -16,3 +16,8 @@ Hint:
        content: "h4tum{sm4ll_key_spac3s_are_deadly}"
        dynamic: true
    files: dynamic # dynamic requires a gen_files script
+   dependencies:
+     type: debian
+     system: ["python3", "libzbar0"] 
+     python: ["pillow", "qrcode", "pyzbar", "numpy", "tqdm"]
+   check: "python3 solve.py"

files/secret_message.txt

@@ -9,7 +9,7 @@ Consider a toy "QR-encryption" scheme where a message is encoded into
 a QR code and then randomized by permuting its tiles with a secret seed.
 
 (a) Under ideal assumptions, explain why this scheme could satisfy
-Kerckhoffs’ principle.  
+Kerckhoffs’libzbar0 principle.  
 (b) Now assume an attacker can test permutations against the QR format
 (find patterns, error correction, alignment markers). Why does this
 reduce the effective security of the scheme?  

gen_files.py

@@ -40,8 +40,8 @@ def scramble_qr_code(payloadList, decoyList, seed):
     return new_qr_code
 
 
-def generate_scrambled_qrcode(seed, output_dir, decoy, name):
-    with open("res/secret_message.txt", "r") as secret:
+def generate_scrambled_qrcode(seed, output_dir, res_dir, decoy, name):
+    with open(res_dir / "secret_message.txt", "r") as secret:
         message = secret.read()
      
     qr_code = generate_qrcode(message + seed)
@@ -49,7 +49,7 @@ def generate_scrambled_qrcode(seed, output_dir, decoy, name):
     qr_pieces = cut_pieces(qr_code)
     decoy_pieces = None
     if decoy:
-        with open("res/decoy.txt", "r") as decoy_msg:
+        with open(res_dir / "decoy.txt", "r") as decoy_msg:
             decoy = decoy_msg.read()
 
         decoy_qr_code = generate_qrcode(decoy)
@@ -65,6 +65,7 @@ def main():
     parser = argparse.ArgumentParser(description="Generates a scrambled QR code with optional decoy pieces.")
     parser.add_argument("seed", type=str, help="The password to scramble the QR code.")
     parser.add_argument("output_dir", type=Path, help="Directory where the output will be stored")
+    parser.add_argument("res_dir", type=Path, help="Directory where needed resources are stored")
     parser.add_argument("--without-decoy", action="store_false", help="Exclude decoy pieces in the scrambled QR code.")
     parser.add_argument("-o", "--output", type=str, default="secret_message.png", help="The name of the output image file.")
     
@@ -73,6 +74,7 @@ def main():
     generate_scrambled_qrcode(
         seed=args.seed, 
         output_dir=args.output_dir,
+        res_dir=args.res_dir,
         decoy=args.without_decoy, 
         name=args.output
     )

healthcheck.py

@@ -12,14 +12,14 @@ test_flag = f"h4tum{{healthy_healthy_healthchecks_{random_bytes}}}"
 
 generate_scrambled_qrcode(
         seed=test_flag, 
-        output_dir=Path("tmp/health_check"),
+        output_dir=Path("/tmp/health_check"),
         decoy=True, 
         name=f"{random_bytes}.png"
 )
 
-output = main(f"tmp/health_check/{random_bytes}.png", False)
+output = main(f"/tmp/health_check/{random_bytes}.png", False)
 
 if output and test_flag in output:
-    print("Healthy!")
+    print(output)
 else:
     print("Oh oh somethings wrong :()")

res/secret_message.txt

@@ -1,4 +0,0 @@
-Wow you solved the challenge!
-Meet us at our booth we really want to get in touch with you :D
-
-Show us the flag: 

solve.py

@@ -1,4 +1,3 @@
-from logging import disable
 from PIL import Image
 from pyzbar.pyzbar import decode
 import itertools
@@ -104,7 +103,7 @@ def solve_combo(combo):
     return None
 
 
-def main(img_path="student_fair/secret_message.png", verbose=True):
+def main(img_path="files/secret_message.png", verbose=True):
     img = Image.open(img_path)
     global new_image
     new_image = Image.new("RGB", (img.height, img.height))
@@ -129,10 +128,8 @@ def main(img_path="student_fair/secret_message.png", verbose=True):
 
     result = None
     
-    MAX_WORKER = 6
-
     # Use `multiprocessing.Pool` with the number of available cores
-    with Pool(MAX_WORKER) as pool:
+    with Pool() as pool:
         # `imap_unordered` returns results as they are completed.
         # This is a lazy iterator, so it doesn't create all combos at once.
         # `tqdm` can still be used to show progress.