add meet me halfway challenge

crypto/MeetMeHalfway/challenge.py

@@ -0,0 +1,53 @@
+
+from random import randint
+from Crypto.Cipher import AES
+from Crypto.Util.Padding import pad
+import json
+
+flag = b'HTB{dummyflag}'
+
+def gen_key(option=0):
+    alphabet = b'0123456789abcdef'
+    const = b'cyb3rXm45!@#'
+    key = b''
+    for i in range(16-len(const)):
+        key += bytes([alphabet[randint(0,15)]])
+
+    if option:
+        return key + const
+    else:
+        return const + key
+
+def encrypt(data, key1, key2):
+    cipher = AES.new(key1, mode=AES.MODE_ECB)
+    ct = cipher.encrypt(pad(data, 16))
+    cipher = AES.new(key2, mode=AES.MODE_ECB)
+    ct = cipher.encrypt(ct)
+    return ct.hex()
+
+
+def challenge():
+    k1 = gen_key()
+    k2 = gen_key(1)
+
+    print(f'key1={k1}; key2={k2}')
+    
+    ct = encrypt(flag, k1, k2)
+    
+    
+    print('Super strong encryption service approved by the elves X-MAS spirit.\n'+\
+                    'Message for all the elves:\n' +ct + '\nEncrypt your text:\n> ')
+    try:
+            
+        dt = json.loads(input().strip())
+        pt = bytes.fromhex(dt['pt'])
+        res = encrypt(pt, k1, k2)
+        print(res + '\n')
+        exit(1)
+    except Exception as e:
+        print(e)
+        print('Invalid payload.\n')
+        exit(1)
+    
+if __name__ == "__main__":
+    challenge()