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blockchain.py

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+# -*- coding: utf-8 -*-
+"""Blockchain.ipynb
+
+Automatically generated by Colaboratory.
+
+Original file is located at
+    https://colab.research.google.com/drive/1wfXS6MTMX2J77EP5X1qFiKQzdo_eh511
+"""
+
+import datetime
+import hashlib
+import json
+ 
+class Blockchain:
+
+    def __init__(self):
+        self.chain = []
+        self.create_block(proof=1, previous_hash='0')
+    
+    def create_block(self, proof, previous_hash):
+        block = {'index': len(self.chain) + 1,
+                 'timestamp': str(datetime.datetime.now()),
+                 'proof': proof,
+                 'previous_hash': previous_hash}
+        self.chain.append(block)
+        return block
+    
+    def print_previous_block(self):
+        return self.chain[-1]
+       
+    def proof_of_work(self, previous_proof):
+        new_proof = 1
+        check_proof = False
+         
+        while check_proof is False:
+            hash_operation = hashlib.sha256(
+                str(new_proof**2 - previous_proof**2).encode()).hexdigest()
+            if hash_operation[:5] == '00000':
+                check_proof = True
+            else:
+                new_proof += 1
+                 
+        return new_proof
+ 
+    def hash(self, block):
+        encoded_block = json.dumps(block, sort_keys=True).encode()
+        return hashlib.sha256(encoded_block).hexdigest()
+ 
+    def chain_valid(self, chain):
+        previous_block = chain[0]
+        block_index = 1
+         
+        while block_index < len(chain):
+            block = chain[block_index]
+            if block['previous_hash'] != self.hash(previous_block):
+                return False
+               
+            previous_proof = previous_block['proof']
+            proof = block['proof']
+            hash_operation = hashlib.sha256(
+                str(proof**2 - previous_proof**2).encode()).hexdigest()
+             
+            if hash_operation[:5] != '00000':
+                return False
+            previous_block = block
+            block_index += 1
+         
+        return True
+
+def create_chain():
+  global blockchain
+  blockchain = Blockchain()
+  return "Chain Instantiated"
+
+def del_chain():
+  global blockchain
+  del blockchain
+  return "Chain Deleted"
+
+def mine_block():
+    previous_block = blockchain.print_previous_block()
+    previous_proof = previous_block['proof']
+    proof = blockchain.proof_of_work(previous_proof)
+    previous_hash = blockchain.hash(previous_block)
+    block = blockchain.create_block(proof, previous_hash)
+     
+    response = {'message': 'A block is MINED',
+                'index': block['index'],
+                'timestamp': block['timestamp'],
+                'proof': block['proof'],
+                'previous_hash': block['previous_hash']}
+     
+    return response
+
+mine_block()
+
+def hack_block(index,value):
+  index=int(index.split(" ")[1])-1
+  blockchain.chain[index]['proof']=value
+  return f"block modified at index:{index+1}"
+
+def display_chain():
+    try:
+      response = {'chain': blockchain.chain,'length': len(blockchain.chain)}
+      
+    except:
+      response = "No chain found"
+    return response
+
+def valid():
+    valid = blockchain.chain_valid(blockchain.chain)
+     
+    if valid:
+        response = {'message': 'The Blockchain is valid.'}
+    else:
+        response = {'message': 'The Blockchain is not valid.'}
+    return response
+
+import gradio as gr
+
+with gr.Blocks(title='Blockchain Simulator') as demo:
+    gr.Image(value="./Blockchain.jpg",show_label=False,shape=(1500,300))
+    with gr.Row():
+        with gr.Column(scale=3):
+            display = gr.Textbox(label="Blockchain Output",lines=5)
+            dblock = gr.Button("Display/Refresh Blockchain")
+        with gr.Column(scale=2):
+            cblock = gr.Button("Instantiate Blockchain")
+            mblock = gr.Button("Mine a Block")
+            vblock = gr.Button("Validate Blockchain")
+            delblock = gr.Button("Delete Blockchain") 
+        with gr.Column(scale=2):
+            index = gr.Radio(choices=["index 1", "index 2", "index 3"],label="Choose an Index to hack")
+            value = gr.Textbox(label="New Value", placeholder = "Enter a Value")
+            hblock = gr.Button("Hack a Block")
+    dblock.click(fn=display_chain, inputs=[], outputs=[display],show_progress=True)
+    cblock.click(fn=create_chain, inputs=[], outputs=[display],show_progress=True)
+    mblock.click(fn=mine_block, inputs=[], outputs=[display],show_progress=True)
+    vblock.click(fn=valid, inputs=[], outputs=[display],show_progress=True)
+    delblock.click(fn=del_chain, inputs=[], outputs=[display],show_progress=True)
+    hblock.click(fn=hack_block, inputs=[index,value], outputs=[display],show_progress=True)
+
+demo.launch()

requirements.txt

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+gradio