diff --git a/common/tools.py b/common/tools.py
index b02c1c4..ccd5973 100644
--- a/common/tools.py
+++ b/common/tools.py
@@ -1,10 +1,23 @@
 import re
-import os
 import logging
 from pathlib import Path
 from common.constants import LOCATOR_LEN_HEX
 
 
+def check_compressed_pk_format(compressed_pk):
+    """
+    Checks if a given value is a 33-byte hex encoded string.
+
+    Args:
+        compressed_pk(:obj:`str`): the value to be checked.
+
+    Returns:
+        :obj:`bool`: Whether or not the value matches the format.
+    """
+
+    return isinstance(compressed_pk, str) and re.match(r"^0[2-3][0-9A-Fa-f]{64}$", compressed_pk) is not None
+
+
 def check_sha256_hex_format(value):
     """
     Checks if a given value is a 32-byte hex encoded string.
diff --git a/teos/gatekeeper.py b/teos/gatekeeper.py
index 0d5131b..2b812fd 100644
--- a/teos/gatekeeper.py
+++ b/teos/gatekeeper.py
@@ -1,5 +1,4 @@
-import re
-
+from common.tools import check_compressed_pk_format
 from common.cryptographer import Cryptographer
 
 
@@ -33,20 +32,6 @@ class Gatekeeper:
         self.default_slots = default_slots
         self.registered_users = {}
 
-    @staticmethod
-    def check_user_pk(user_pk):
-        """
-        Checks if a given value is a 33-byte hex encoded string.
-
-        Args:
-            user_pk(:obj:`str`): the value to be checked.
-
-        Returns:
-            :obj:`bool`: Whether or not the value matches the format.
-        """
-
-        return isinstance(user_pk, str) and re.match(r"^[0-9A-Fa-f]{66}$", user_pk) is not None
-
     def add_update_user(self, user_pk):
         """
         Adds a new user or updates the subscription of an existing one, by adding additional slots.
@@ -58,7 +43,7 @@ class Gatekeeper:
             :obj:`int`: the number of available slots in the user subscription.
         """
 
-        if not self.check_user_pk(user_pk):
+        if not check_compressed_pk_format(user_pk):
             raise ValueError("provided public key does not match expected format (33-byte hex string)")
 
         if user_pk not in self.registered_users: