ALL the CTFS of Crypto2025 finally

crypto-simmetric/decrypt_it_if_you_are_fast_enough/chall.py

@@ -0,0 +1,31 @@
+import os
+import random
+from time import time
+from Crypto.Cipher import ChaCha20
+from Crypto.Util.number import long_to_bytes
+from secret import flag
+
+key = os.urandom(32)
+
+
+def encrypt(msg):
+    random.seed(int(time()))
+    cipher = ChaCha20.new(
+        key=key, nonce=long_to_bytes(random.getrandbits(12*8)))
+    return cipher.encrypt(msg.encode())
+
+
+def main():
+
+    confirm = input("Want to encrypt? (y/n/f)")
+    while confirm.lower() != 'n':
+        if confirm.lower() == 'y':
+            msg = input("> ")
+            print(encrypt(msg).hex())
+        elif confirm.lower() == 'f':
+            print(encrypt(flag).hex())
+        confirm = input("Want to encrypt something else? (y/n/f)")
+
+
+if __name__ == '__main__':
+    main()