fixes transactions

goodchain/src/helpers/SignatureHelper.py

@@ -3,6 +3,7 @@ from cryptography.hazmat.primitives.asymmetric import rsa
 from cryptography.hazmat.primitives import serialization
 from cryptography.hazmat.primitives import hashes
 from cryptography.hazmat.primitives.asymmetric import padding
+from cryptography.hazmat.backends import default_backend
 
 def generateKeys():
     private_key = rsa.generate_private_key(public_exponent=65537,key_size=2048)
@@ -43,29 +44,31 @@ def bytesToKeys(private_ser, public_ser):
 
 def publicBytesToKey(public_ser):
     public_key = serialization.load_pem_public_key(
-        public_ser
+        public_ser,
+        backend=default_backend()
     )
     return public_key
 
 def privateBytesToKey(private_ser):
     private_key = serialization.load_pem_private_key(
         private_ser,
-        password=None
+        password=None,
+        backend=default_backend()
     )
     return private_key
 
 def sign(message, private_key):
     message = bytes(str(message), 'utf-8')
-    key = privateBytesToKey(private_key)
-    signature = key.sign(
+    signature = private_key.sign(
         message,
         padding.PSS(mgf=padding.MGF1(hashes.SHA256()), salt_length=padding.PSS.MAX_LENGTH),
         hashes.SHA256()
         )
     return signature
 
-def verify(message, signature, public_key):
+def verify(message, signature, public_ser):
     message = bytes(str(message), 'utf-8')
+    public_key = publicBytesToKey(public_ser)
     try:
         public_key.verify(
             signature,