t01 finished from lesson 5

period_1/05-transaction/501_T01_A01_Sign_Data/Signature.py

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+
+# This tutorial is already done in lesson 3
+# You can copy and paste the completed signature module
+
+"""Asymmetric Cryptography -> Digital Signature: Tutorial 4
+
+The goal of this tutorial is to learn how to sign and verify messages using asymmetric keys.
+In this implementation the passed message as an argument is a string that needs to be converted to a byte object.
+When signing a message the RSA sign-function requires a specific hash like SHA256, and padding such as PSS. 
+Be aware that verification must use the same algorithms values to correctly verify the signature.
+
+Your task is to:
+    * locate the TODOs in this file
+    * complete the missing part from the code 
+    * run the test of this tutorial located in same folder.
+
+To test run 'Signature_t.py' in your command line
+
+Notes:
+    * do not change class structure or method signature to not break unit tests
+    * visit this url for more information on this topic:
+    https://cryptography.io/en/latest/hazmat/primitives/asymmetric/rsa/
+"""
+
+from cryptography.exceptions import *
+from cryptography.hazmat.primitives.asymmetric import rsa
+from cryptography.hazmat.primitives import hashes
+from cryptography.hazmat.primitives.asymmetric import padding
+
+def generate_keys():
+    private_key = rsa.generate_private_key(public_exponent=65537,key_size=2048)
+    public_key = private_key.public_key()
+    return private_key, public_key
+
+def sign(message, private_key):
+    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):
+    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

period_1/05-transaction/501_T01_A01_Sign_Data/Transaction_t_a.py

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+"""
+This test case will verify if the provided exercise solution by a student for the Signature.py is correct.
+
+The goal of this tutorial is to learn how to create text-based unformatted transactions.
+However, in real scenario, we need to use a more specific and useful format for transactions (next tutorial).
+
+
+Your task is to:
+    * locate the TODOs in this file
+    * complete the missing part from the code 
+    * run this test file and observe the results.
+
+"""
+
+from Signature import *
+
+if __name__ == '__main__':
+    
+    alex_prv, alex_pbc = generate_keys()
+    mike_prv, mike_pbc = generate_keys()
+
+    data = [
+        'Alex pays 2 coin to mike', 
+        'Alex pays 1.2 coins to Mara', 
+        'Mike pays 0.6 coin to Alex'
+        ]
+
+
+
+    # TODO 1: Complete the test case 1
+    # Create a test case to sign data using alex's signature 
+    # and then try to verify it using the same (alex's) signature
+    # As data is signed by alex signature, it should be successfully verified by alex's key
+    
+    # sign data with alexs signature
+    alex_data = sign(data[0].encode(), alex_prv)
+
+    # verify data with alexs signature
+    if verify(data[0].encode(), alex_data, alex_pbc):
+        print('Success: Valid signature is verified.')
+    else:
+        print('Failed: Invalid signature is not verified.')
+
+    # Test case 1: write your code here:
+   
+
+    
+
+
+
+
+
+
+    # TODO 2: Complete the test case 2
+    # Create a test case to sign data using alex's signature 
+    # and then try to verify it using mike's signature
+    # As data is signed by alex signature, it should not be successfully verified by mike's (or any other key) key
+    
+    # Test case 2: write your code here:
+    if verify(data[0].encode(), alex_data, mike_pbc):
+        print('Failed: Valid signature is verified.')
+    else:
+        print('Success: Invalid signature is not verified.')

period_1/05-transaction/501_T01_A01_Sign_Data/output.txt

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+Success: Valid signature is verified.
+Success: Inalid signature is not verified.