fix for stable reversible pseudonym

Author: gerbrand-bosch

app/services/pseudonym_service.py

@@ -79,7 +79,8 @@ def encode_pseudonym(self, pseudonym: str) -> str:
         Encode the personal ID using AES encryption in CBC mode with PKCS7 padding.
         """
         try:
-            iv = get_random_bytes(AES.block_size)
+            iv_input = hashlib.sha256("|".join(pseudonym.split('|')[:-2]).encode('utf-8')).digest()
+            iv = iv_input[:AES.block_size]
             message = f"{pseudonym}".encode('utf-8')
             cipher = AES.new(self.__aes_key, AES.MODE_GCM, iv)
             ciphertext = cipher.encrypt(pad(message, AES.block_size))