finished lesson lesson 5.3

period_1/05-transaction/503_T03_A03_Transaction_Sign/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
+
+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/503_T03_A03_Transaction_Sign/Transaction.py

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+#!/usr/bin/env python3
+"""
+Transaction Class - Definition of Input and Output
+
+This is just a copy of the previous tutorial. If you have already completed the previous tutorial,
+simply copy and paste the code of transaction class, here.
+
+Check the test file. It includes signing and verification of transactions
+using this new defined transaction class. 
+"""
+
+from Signature import *
+
+class Tx:
+
+    def __init__(self):
+        self.inputs = []
+        self.outputs = []
+
+
+
+
+    # TODO 2: Complete the method
+
+    def add_input(self, from_addr, amount):
+        self.inputs.append([from_addr, amount])
+
+    # TODO 3: Complete the method
+
+    def add_output(self, to_addr, amount):
+        self.outputs.append([to_addr, amount])

period_1/05-transaction/503_T03_A03_Transaction_Sign/Transaction_t.py

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+"""
+This test case will verify if the provided exercise solution by a student for the Transaction.py is correct.
+"""
+
+from Signature import *
+from Transaction import *
+
+
+def print_transaction(tx_name, tx):
+    print('---------------')
+    print(f'-- {tx_name}')
+
+    for (index, input_item) in enumerate(tx.inputs):
+        for key_name, prv_key, pbc_key in keys_list:
+            if pbc_key == input_item[0]:
+                payer = key_name
+        print(f'In[{index+1}]:  {payer} sends {input_item[1]} coin')
+
+    for (index, output_item) in enumerate(tx.outputs):
+        for key_name, prv_key, pbc_key in keys_list:
+            if pbc_key == output_item[0]:
+                receiver = key_name
+        print(f'Out[{index+1}]: {receiver} receives {output_item[1]} coin') 
+    print()
+
+
+if __name__ == '__main__':
+    
+    keys_list =[]
+
+    alex_prv, alex_pbc = generate_keys()
+    keys_list.append(('alex', alex_prv, alex_pbc))
+
+    mike_prv, mike_pbc = generate_keys()
+    keys_list.append(('mike', mike_prv, mike_pbc))
+
+    rose_prv, rose_pbc = generate_keys()
+    keys_list.append(('rose', rose_prv, rose_pbc))
+
+    mara_prv, mara_pbc = generate_keys()
+    keys_list.append(('mara', mara_prv, mara_pbc))
+
+    Tx1 = Tx()
+    Tx1.add_input(alex_pbc, 0.9)
+    Tx1.add_output(mike_pbc, 0.8)
+    print_transaction('Tx1', Tx1)
+
+    Tx1_alex_signature = sign(bytes(str(Tx1), 'utf-8'), alex_prv)
+    verified = verify(bytes(str(Tx1), 'utf-8'), Tx1_alex_signature, alex_pbc)
+    if verified:
+        print('Success: Valid signature is verified.')
+    else:
+        print('Fail: Valid signature is not verified.')
+
+    # if mike sign it to perform illegal transfer
+    Tx1_mike_signature = sign(bytes(str(Tx1), 'utf-8'), mike_prv)
+    verified = verify(bytes(str(Tx1), 'utf-8'), Tx1_mike_signature, alex_pbc)
+    if verified:
+        print('Fail: Invalid signature is accepted.')
+    else:
+        print('Success: Invalid signature is not verified.')
+
+
+    Tx2 = Tx()
+    Tx2.add_input(alex_pbc, 2.1)
+    Tx2.add_output(mike_pbc, 0.9)
+    Tx2.add_output(rose_pbc, 1.0)
+    Tx2.add_input(mara_pbc, 0.7)
+    Tx2.add_input(mara_pbc, 1.1)
+    Tx2.add_input(mara_pbc, 1.5)
+    Tx2.add_output(mike_pbc, 1.9)
+    Tx2.add_output(rose_pbc, 0.2)
+    print_transaction('Tx2', Tx2)
+
+    Tx2_alex_signature = sign(bytes(str(Tx2), 'utf-8'), alex_prv)
+    Tx2_mara_signature = sign(bytes(str(Tx2), 'utf-8'), mara_prv)
+
+    alex_verified = verify(bytes(str(Tx2), 'utf-8'), Tx2_alex_signature, alex_pbc)
+    mara_verified = verify(bytes(str(Tx2), 'utf-8'), Tx2_mara_signature, mara_pbc)
+
+    if alex_verified and mara_verified:
+        print('Success: A valid Transaction is verified.')
+    else:
+        print('Fail: A Valid Transaction is not verified.')
+
+
+    Tx2_alex_signature = sign(bytes(str(Tx2), 'utf-8'), alex_prv)
+    Tx2_mike_signature = sign(bytes(str(Tx2), 'utf-8'), mike_prv)
+
+    alex_verified = verify(bytes(str(Tx2), 'utf-8'), Tx2_alex_signature, alex_pbc)
+    mara_verified = verify(bytes(str(Tx2), 'utf-8'), Tx2_mike_signature, mara_pbc)
+
+    if alex_verified and mara_verified:
+        print('Fail: An Invalid Transaction is not verified.')
+    else:
+        print('Success: An Invalid Transaction is not verified.')

period_1/05-transaction/503_T03_A03_Transaction_Sign/output.txt

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+---------------
+-- Tx1
+In[1]:  alex sends 0.9 coin
+Out[1]: mike receives 0.8 coin
+
+Success: Valid signature is verified.
+Success: Invalid signature is not verified.
+---------------
+-- Tx2
+In[1]:  alex sends 2.1 coin
+In[2]:  mara sends 0.7 coin
+In[3]:  mara sends 1.1 coin
+In[4]:  mara sends 1.5 coin
+Out[1]: mike receives 0.9 coin
+Out[2]: rose receives 1.0 coin
+Out[3]: mike receives 1.9 coin
+Out[4]: rose receives 0.2 coin
+
+Success: A valid Transaction is verified.
+Success: An Invalid Transaction is not verified.