b1

import hashlib
import datetime

class Block:
    def __init__(self, index, timestamp, owner, previous_hash):
        self.index = index
        self.timestamp = timestamp
        self.owner = owner
        self.previous_hash = previous_hash
        self.hash = self.calculate_hash()

    def calculate_hash(self):
        data = str(self.index) + str(self.timestamp) + str(self.owner) + str(self.previous_hash)
        sha = hashlib.sha256()
        sha.update(data.encode('utf-8'))
        return sha.hexdigest()

class Blockchain:
    def __init__(self):
        self.chain = [self.create_genesis_block()]

    def create_genesis_block(self):
        return Block(0, datetime.datetime.now(), "Original Owner", "0")

    def get_latest_block(self):
        return self.chain[-1]

    def add_block(self, new_block):
        new_block.previous_hash = self.get_latest_block().hash
        new_block.hash = new_block.calculate_hash()
        self.chain.append(new_block)

    def is_valid(self):
        for i in range(1, len(self.chain)):
            current_block = self.chain[i]
            previous_block = self.chain[i-1]
            if current_block.hash != current_block.calculate_hash():
                return False
            if current_block.previous_hash != previous_block.hash:
                return False
        return True