HEDU-Currency.py

import hashlib

import time

class Block:

    def __init__(self, index, proof_no, prev_hash, data, timestamp=None):

        self.index = index

        self.proof_no = proof_no

        self.prev_hash = prev_hash

        self.data = data

        self.timestamp = timestamp or time.time()

    @property

    def calculate_hash(self):

        block_of_string = "{}{}{}{}{}".format(self.index, self.proof_no,

                                              self.prev_hash, self.data,

                                              self.timestamp)

        return hashlib.sha256(block_of_string.encode()).hexdigest()

    def __repr__(self):

        return "{} - {} - {} - {} - {}".format(self.index, self.proof_no,

                                               self.prev_hash, self.data,

                                               self.timestamp)

class BlockChain:

    def __init__(self):

        self.chain = []

        self.current_data = []

        self.nodes = set()

        self.construct_genesis()

    def construct_genesis(self):

        self.construct_block(proof_no=0, prev_hash=0)

    def construct_block(self, proof_no, prev_hash):

        block = Block(

            index=len(self.chain),

            proof_no=proof_no,

            prev_hash=prev_hash,

            data=self.current_data)

        self.current_data = []

        self.chain.append(block)

        return block

    @staticmethod

    def check_validity(block, prev_block):

        if prev_block.index + 1 != block.index:

            return False

        elif prev_block.calculate_hash != block.prev_hash:

            return False

        elif not BlockChain.verifying_proof(block.proof_no,

                                            prev_block.proof_no):

            return False

        elif block.timestamp <= prev_block.timestamp:

            return False

        return True

    def new_data(self, sender, recipient, quantity):

        self.current_data.append({

            'sender': sender,

            'recipient': recipient,

            'quantity': quantity

        })

        return True

    @staticmethod

    def proof_of_work(last_proof):

        '''this simple algorithm identifies a number f' such that hash(ff') contain 4 leading zeroes

         f is the previous f'

         f' is the new proof

        '''

        proof_no = 0

        while BlockChain.verifying_proof(proof_no, last_proof) is False:

            proof_no += 1

        return proof_no

    @staticmethod

    def verifying_proof(last_proof, proof):

        #verifying the proof: does hash(last_proof, proof) contain 4 leading zeroes?

        guess = f'{last_proof}{proof}'.encode()

        guess_hash = hashlib.sha256(guess).hexdigest()

        return guess_hash[:4] == "0000"

    @property

    def latest_block(self):

        return self.chain[-1]

    def block_mining(self, details_miner):

        self.new_data(

            sender="0",  #it implies that this node has created a new block

            recipient=details_miner,

            quantity=

            1,  #creating a new block (or identifying the proof number) is awarded with 1

        )

        last_block = self.latest_block

        last_proof_no = last_block.proof_no

        proof_no = self.proof_of_work(last_proof_no)

        last_hash = last_block.calculate_hash

        block = self.construct_block(proof_no, last_hash)

        return vars(block)

    def create_node(self, address):

        self.nodes.add(address)

        return True

    @staticmethod

    def obtain_block_object(block_data):

        #obtains block object from the block data

        return Block(

            block_data['index'],

            block_data['proof_no'],

            block_data['prev_hash'],

            block_data['data'],

            timestamp=block_data['timestamp'])