Initial commit

.vscode/launch.json

@@ -0,0 +1,25 @@
+{
+    // Use IntelliSense to learn about possible attributes.
+    // Hover to view descriptions of existing attributes.
+    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
+    "version": "0.2.0",
+    "configurations": [
+        {
+            "name": "Python: Flask",
+            "type": "python",
+            "request": "launch",
+            "module": "flask",
+            "env": {
+                "FLASK_APP": "app.py",
+                "FLASK_DEBUG": "1"
+            },
+            "args": [
+                "run",
+                "--no-debugger",
+                "--no-reload"
+            ],
+            "jinja": true,
+            "justMyCode": true
+        }
+    ]
+}

blockchain.py

@@ -0,0 +1,187 @@
+import hashlib
+import json
+
+from time import time
+from uuid import uuid4
+
+from flask import Flask
+
+class Blockchain(object):
+    def __init__(self):
+        self.chain = []
+        self.current_transactions = []
+
+        # Create the genesis block
+        self.new_block(previous_hash=1, proof=100)
+
+    def proof_of_work(self, last_proof):
+        """
+        Simple Proof of Work Algorithm:
+         - Find a number p' such that hash(pp') contains leading 4 zeroes, where p is the previous p'
+         - p is the previous proof, and p' is the new proof
+        :param last_proof: <int>
+        :return: <int>
+        """
+
+        proof = 0
+        while self.valid_proof(last_proof, proof) is False:
+            proof += 1
+
+        return proof
+
+    @staticmethod
+    def valid_proof(last_proof, proof):
+        """
+        Validates the Proof: Does hash(last_proof, proof) contain 4 leading zeroes?
+        :param last_proof: <int> Previous Proof
+        :param proof: <int> Current Proof
+        :return: <bool> True if correct, False if not.
+        """
+
+        guess = f'{last_proof}{proof}'.encode()
+        guess_hash = hashlib.sha256(guess).hexdigest()
+        return guess_hash[:4] == "0000"
+
+    def new_block(self, proof, previous_hash=None):
+        """
+        Create a new Block in the Blockchain
+        :param proof: <int> The proof given by the Proof of Work algorithm
+        :param previous_hash: (Optional) <str> Hash of previous Block
+        :return: <dict> New Block
+        """
+
+        block = {
+            'index': len(self.chain) + 1,
+            'timestamp': time(),
+            'transactions': self.current_transactions,
+            'proof': proof,
+            'previous_hash': previous_hash or self.hash(self.chain[-1]),
+        }
+
+        # Reset the current list of transactions
+        self.current_transactions = []
+
+        self.chain.append(block)
+        return block
+
+    def new_transaction(self, sender, recipient, amount):
+        """
+        Creates a new transaction to go into the next mined Block
+        :param sender: <str> Address of the Sender
+        :param recipient: <str> Address of the Recipient
+        :param amount: <int> Amount
+        :return: <int> The index of the Block that will hold this transaction
+        """
+        self.current_transactions.append({
+            'sender': sender,
+            'recipient': recipient,
+            'amount': amount,
+        })
+
+        return self.last_block['index'] + 1
+
+    @property
+    def last_block(self):
+        return self.chain[-1]
+
+    @staticmethod
+    def hash(block):
+        """
+        Creates a SHA-256 hash of a Block
+        :param block: <dict> Block
+        :return: <str>
+        """
+
+        # We must make sure that the Dictionary is Ordered, or we'll have inconsistent hashes
+        block_string = json.dumps(block, sort_keys=True).encode()
+        return hashlib.sha256(block_string).hexdigest()
+
+    def new_transaction(self, sender, recipient, amount):
+        """
+        Creates a new transaction to go into the next mined Block
+        :param sender: <str> Address of the Sender
+        :param recipient: <str> Address of the Recipient
+        :param amount: <int> Amount
+        :return: <int> The index of the Block that will hold this transaction
+        """
+
+        self.current_transactions.append({
+            'sender': sender,
+            'recipient': recipient,
+            'amount': amount,
+        })
+
+        return self.last_block['index'] + 1    
+
+# Instantiate our Node
+app = Flask(__name__)
+
+# Generate a globally unique address for this node
+node_identifier = str(uuid4()).replace('-', '')
+
+# Instantiate the Blockchain
+blockchain = Blockchain()
+
+
+@app.route('/mine', methods=['GET'])
+def mine():
+    return "We'll mine a new Block"
+
+@app.route('/transactions/new', methods=['POST'])
+def new_transaction():
+    return "We'll add a new transaction"
+
+@app.route('/chain', methods=['GET'])
+def full_chain():
+    response = {
+        'chain': blockchain.chain,
+        'length': len(blockchain.chain),
+    }
+    return jsonify(response), 200
+
+if __name__ == '__main__':
+    app.run(host='0.0.0.0', port=5000)
+
+@app.route('/transactions/new', methods=['POST'])
+def new_transaction():
+    values = request.get_json()
+
+    # Check that the required fields are in the POST'ed data
+    required = ['sender', 'recipient', 'amount']
+    if not all(k in values for k in required):
+        return 'Missing values', 400
+
+    # Create a new Transaction
+    index = blockchain.new_transaction(values['sender'], values['recipient'], values['amount'])
+
+    response = {'message': f'Transaction will be added to Block {index}'}
+    return jsonify(response), 201        
+
+@app.route('/mine', methods=['GET'])
+def mine():
+    # We run the proof of work algorithm to get the next proof...
+    last_block = blockchain.last_block
+    last_proof = last_block['proof']
+    proof = blockchain.proof_of_work(last_proof)
+
+    # We must receive a reward for finding the proof.
+    # The sender is "0" to signify that this node has mined a new coin.
+    blockchain.new_transaction(
+        sender="0",
+        recipient=node_identifier,
+        amount=1,
+    )
+
+    # Forge the new Block by adding it to the chain
+    previous_hash = blockchain.hash(last_block)
+    block = blockchain.new_block(proof, previous_hash)
+
+    response = {
+        'message': "New Block Forged",
+        'index': block['index'],
+        'transactions': block['transactions'],
+        'proof': block['proof'],
+        'previous_hash': block['previous_hash'],
+    }
+
+    return jsonify(response), 200