diff --git a/scripts/mbedtls_dev/crypto_knowledge.py b/scripts/mbedtls_dev/crypto_knowledge.py
index f93ca55..d37e0b5 100644
--- a/scripts/mbedtls_dev/crypto_knowledge.py
+++ b/scripts/mbedtls_dev/crypto_knowledge.py
@@ -20,7 +20,7 @@
 
 import enum
 import re
-from typing import Dict, Iterable, Optional, Pattern, Tuple
+from typing import Iterable, Optional, Tuple
 
 from mbedtls_dev.asymmetric_key_data import ASYMMETRIC_KEY_DATA
 
@@ -176,21 +176,6 @@
         return b''.join([self.DATA_BLOCK] * (length // len(self.DATA_BLOCK)) +
                         [self.DATA_BLOCK[:length % len(self.DATA_BLOCK)]])
 
-    KEY_TYPE_FOR_SIGNATURE = {
-        'PSA_KEY_USAGE_SIGN_HASH': re.compile('.*KEY_PAIR'),
-        'PSA_KEY_USAGE_VERIFY_HASH': re.compile('.*KEY.*')
-    } #type: Dict[str, Pattern]
-    """Use a regexp to determine key types for which signature is possible
-       when using the actual usage flag.
-    """
-    def is_valid_for_signature(self, usage: str) -> bool:
-        """Determine if the key type is compatible with the specified
-           signitute type.
-
-        """
-        # This is just temporaly solution for the implicit usage flags.
-        return re.match(self.KEY_TYPE_FOR_SIGNATURE[usage], self.name) is not None
-
     def can_do(self, alg: 'Algorithm') -> bool:
         """Whether this key type can be used for operations with the given algorithm.