diff --git a/common/cryptographer.py b/common/cryptographer.py
index 18cca23..512fff6 100644
--- a/common/cryptographer.py
+++ b/common/cryptographer.py
@@ -124,7 +124,7 @@ class Cryptographer:
             raise ValueError("Wrong return type. Return type must be 'hex' 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:
@@ -138,7 +138,7 @@ class Cryptographer:
     @staticmethod
     def verify(message, signature, pk):
         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 d89bbdf..66aeb2c 100644
--- a/common/tools.py
+++ b/common/tools.py
@@ -2,4 +2,4 @@ import re
 
 
 def check_sha256_hex_format(value):
-    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