diff --git a/common/cryptographer.py b/common/cryptographer.py
index 873df97..93fc72a 100644
--- a/common/cryptographer.py
+++ b/common/cryptographer.py
@@ -246,7 +246,7 @@ class Cryptographer:
             raise ValueError("Wrong return type. Return type must be 'str' or 'bytes'")
 
         if not isinstance(sk, ec.EllipticCurvePrivateKey):
-            logger.error("Wrong public key.")
+            logger.error("The value passed as sk is not a private key (EllipticCurvePrivateKey).")
             return None
 
         else:
@@ -274,7 +274,7 @@ class Cryptographer:
         """
 
         if not isinstance(pk, ec.EllipticCurvePublicKey):
-            logger.error("Wrong public key.")
+            logger.error("The value passed as pk is not a public key (EllipticCurvePublicKey).")
             return False
 
         if isinstance(signature, str):
diff --git a/common/tools.py b/common/tools.py
index 634e7a4..6d539b1 100644
--- a/common/tools.py
+++ b/common/tools.py
@@ -11,4 +11,4 @@ def check_sha256_hex_format(value):
     Returns:
         :mod:`bool`: Wether or not the value matches the format.
     """
-    return isinstance(value, str) and re.search(r"^[0-9A-Fa-f]{64}$", value) is not None
+    return isinstance(value, str) and re.match(r"^[0-9A-Fa-f]{64}$", value) is not None