def create_genesis_block(): # Manually construct a block with # index zero and arbitrary previous hash return Block(0, date.datetime.now(), "Genesis Block", "0")
# Create the blockchain and add the genesis block blockchain = [create_genesis_block()] previous_block = blockchain[0]
# How many blocks should we add to the chain # after the genesis block num_of_blocks_to_add = 20
# Add blocks to the chain for i in range(0, num_of_blocks_to_add): block_to_add = next_block(previous_block) blockchain.append(block_to_add) previous_block = block_to_add # Tell everyone about it! print "Block #{} has been added to the blockchain!".format(block_to_add.index) print "Hash: {}\n".format(block_to_add.hash)
from flask import Flask from flask import request node = Flask(__name__)
# Store the transactions that # this node has in a list this_nodes_transactions = []
@node.route('/txion', methods=['POST']) deftransaction(): if request.method == 'POST': # On each new POST request, # we extract the transaction data new_txion = request.get_json() # Then we add the transaction to our list this_nodes_transactions.append(new_txion) # Because the transaction was successfully # submitted, we log it to our console print"New transaction" print"FROM: {}".format(new_txion['from']) print"TO: {}".format(new_txion['to']) print"AMOUNT: {}\n".format(new_txion['amount']) # Then we let the client know it worked out return"Transaction submission successful\n"
defproof_of_work(last_proof): # Create a variable that we will use to find # our next proof of work incrementor = last_proof + 1 # Keep incrementing the incrementor until # it's equal to a number divisible by 9 # and the proof of work of the previous # block in the chain whilenot (incrementor % 9 == 0and incrementor % last_proof == 0): incrementor += 1 # Once that number is found, # we can return it as a proof # of our work return incrementor
@node.route('/mine', methods = ['GET']) defmine(): # Get the last proof of work last_block = blockchain[len(blockchain) - 1] last_proof = last_block.data['proof-of-work'] # Find the proof of work for # the current block being mined # Note: The program will hang here until a new # proof of work is found proof = proof_of_work(last_proof) # Once we find a valid proof of work, # we know we can mine a block so # we reward the miner by adding a transaction this_nodes_transactions.append( { "from": "network", "to": miner_address, "amount": 1 } ) # Now we can gather the data needed # to create the new block new_block_data = { "proof-of-work": proof, "transactions": list(this_nodes_transactions) } new_block_index = last_block.index + 1 new_block_timestamp = this_timestamp = date.datetime.now() last_block_hash = last_block.hash # Empty transaction list this_nodes_transactions[:] = [] # Now create the # new block! mined_block = Block( new_block_index, new_block_timestamp, new_block_data, last_block_hash ) blockchain.append(mined_block) # Let the client know we mined a block return json.dumps({ "index": new_block_index, "timestamp": str(new_block_timestamp), "data": new_block_data, "hash": last_block_hash }) + "\n"
@node.route('/blocks', methods=['GET']) def get_blocks(): chain_to_send = blockchain # Convert our blocks into dictionaries # so we can send them as json objects later for block in chain_to_send: block_index = str(block.index) block_timestamp = str(block.timestamp) block_data = str(block.data) block_hash = block.hash block = { "index": block_index, "timestamp": block_timestamp, "data": block_data, "hash": block_hash } # Send our chain to whomever requested it chain_to_send = json.dumps(chain_to_send) return chain_to_send
def find_new_chains(): # Get the blockchains of every # other node other_chains = [] for node_url in peer_nodes: # Get their chains using a GET request block = requests.get(node_url + "/blocks").content # Convert the JSON object to a Python dictionary block = json.loads(block) # Add it to our list other_chains.append(block) return other_chains
def consensus(): # Get the blocks from other nodes other_chains = find_new_chains() # If our chain isn't longest, # then we store the longest chain longest_chain = blockchain for chain in other_chains: if len(longest_chain) < len(chain): longest_chain = chain # If the longest chain wasn't ours, # then we set our chain to the longest blockchain = longest_chain
