Blockchain in python using functions
There are a total of 10 functions involved in this project ,per-requisites basic blockchain lingo should be known , The project is divided into sub parts , we will traverse sub -parts wise ;
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1.Genesis_block :
#Gensis block initialization genesis_block = { 'previous_hash': '', 'index': 0, 'transaction': [], 'nonce': 0 #It is used in mining process } #Declaring Gensis Block blockchain = [genesis_block]2.Adding a Transaction
tx_data = get_transaction_value() sender,recipient, amount = tx_data add_value(recipient,sender, amount=amount) print(open_transactions) #open_transactions is a list of all the transactions that have happened and minedA.Now here get_transaction_value is used to take input from the user
def get_transaction_value(): tx_sender=input('Enter the sender of the transaction:') tx_recipient = input('Enter the recipient of the transaction: ') tx_amount = float(input('Enter your transaction amount ')) return tx_sender,tx_recipient, tx_amountB.Add transaction , which will later be verified by Miners . Here we use a dictionary as key — value paring is required ,after which we append transaction into open_transaction list
def add_value(recipient, sender, amount=1.0): transaction = {'sender': sender, 'recipient': recipient, 'amount': amount} open_transactions.append(transaction)3.Mining blocks , It is used to verify the transaction(i.e -> proof of work ) and then if everything works ,then add transaction to the longest Blockchain .
def mine_block(): last_block = blockchain[-1] hashed_block = hash_block(last_block) #we compare the value of hash of the last block and value of hash stored in the present block of the last block , # if they are not same that means blockchain has been modified nonce = pow() #To proof of work to check for transaction verification reward_transaction = { 'sender': 'MINING', 'recipient': owner, 'amount': reward } #Adding the mining transaction open_transactions.append(reward_transaction) block = { 'previous_hash': hashed_block, 'index': len(blockchain), 'transaction': open_transactions, 'nonce': nonce } blockchain.append(block)A.Proof of Work or pow :It is used to return the value of nonce (unique id ) , after each transaction is valid , if not valid it keeps on increasing the value of nonce.
last_block = blockchain[-1] last_hash = hash_block(last_block) #storing details of previous hash nonce = 0 #initialized the nonce to zero while not valid_proof(open_transactions, last_hash, nonce): #value of nonce is incremented when the transaction is verified nonce += 1 return nonceA.1 valid_proof : There is a pattern in hash value of blocks of same Blockchain, We verify that pattern to check which blockchain does block belong
def valid_proof(transactions, last_hash, nonce): guess = (str(transactions) + str(last_hash) + str(nonce)).encode() guess_hash = hashlib.sha256(guess).hexdigest() #generating a Hashcode for a particular verified Transaction last_chars = guess_hash[-10:] #We have reduced the print to last 10 characters of each verification print(last_chars) #if first 4 characters is equal to 2018 , it means it belongs to this specific blockchain return guess_hash[-4:] == '2018'4. Hashing : We use sha_256 hashing as it is standard hashing function , you can also Use sha3_256 it is modified function of sha_256
def hash_block(block): return hashlib.sha256(json.dumps(block).encode()).hexdigest() #1.sha 256-> SHA-256 is a one-way function that converts a text of any length into a string of 256 bits. #2.encode()-> Used to encode the string into hexidigest format #3.hexidigest()-> string is returned as a string of double length , containg only hexadecimal digits.You can integrate it with Web framework to make an executable version of this , e.x -> Flask , Django ,etc.
GitHub Link: https://github.com/kakabisht/Blockchain-implementation-without-networkingpart
Originally published at http://programmerprodigy.code.blog on April 4, 2020.
