added all tutorials from lesson 7

period_1/07-mining/703_TX2_A02_Nonce - tamper test/Signature.py

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+from cryptography.exceptions import *
+from cryptography.hazmat.primitives.asymmetric import rsa
+from cryptography.hazmat.primitives import hashes
+from cryptography.hazmat.primitives.asymmetric import padding
+from cryptography.hazmat.primitives import serialization
+
+def generate_keys():
+    private_key = rsa.generate_private_key(public_exponent=65537,key_size=2048)
+    public_key = private_key.public_key()
+
+    pbc_ser = public_key.public_bytes(
+        encoding=serialization.Encoding.PEM,
+        format=serialization.PublicFormat.SubjectPublicKeyInfo)
+    return private_key, pbc_ser
+
+def sign(message, private_key):
+    message = bytes(str(message), 'utf-8')
+    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, pbc_ser):
+    message = bytes(str(message), 'utf-8')
+    public_key = serialization.load_pem_public_key(pbc_ser)
+    try:
+        public_key.verify(
+            signature,
+            message,
+            padding.PSS(mgf=padding.MGF1(hashes.SHA256()),
+            salt_length=padding.PSS.MAX_LENGTH),
+            hashes.SHA256()
+            )
+        return True
+    except InvalidSignature:
+         return False
+    except:
+        print("Error executing 'public_key.verify'")
+        return False