Blockchain brought about an innovative way of solving problems using decentralized technology. It involves a series of cryptographic blocks linked together through hashes. The following are some characteristics of blockchain:
Immutability: Data stored on a blockchain cannot be changed.
Decentralized technology: No single authority controls the system.
Secure: All the records in the blockchain are individually encrypted.
We'll mainly focus on implementing the basics of a blockchain with Python. First, we start with the Block class.
We use the concept of object-oriented programming to create a class that would consist of the different properties of a block. Each block contains a cryptographic hash of the previous block, a timestamp, and transaction data.
class Block:def __init__(self, data, previous_hash):self.timestamp = datetime.now()self.data = dataself.hash = self.calc_hash()self.previous_hash = previous_hashself.next = None
timestamp: We use the datetime module to create get the current date and time and create the block.
from datetime import datetime
From datetime.now(), we get the timestamp property.
data: We'll store the data in a string format.
hash: For each block, we generate a new hash using the SHA-256 hashing algorithm.
We need to import the hashlib library for encryption.
import hashlibdef calc_hash(self):hash_str = "{}{}{}".format(self.timestamp, self.data, self.previous_hash).encode('utf-8')return hashlib.sha256(hash_str).hexdigest()
The function accepts the data as a string and then encodes it, we use the SHA256() function for encryption after which it is converted into a hexadecimal string.
previous_hash: This contains the hash value of the previous block.
A blockchain consists of different blocks that are linked together. To link each block together, we use a linked list.
We initialize the list with the head node and next pointer.
class Blockchain:def __init__(self):self.head = Noneself.next = None
Next, we create add_block to add each successive block to the chain.
def add_block(self, data):if self.head == None:self.head = Block(data,0)else:current = self.head# starts a loopwhile current.next:current = current.next# stores the previous has for the next blockprevious_hash = current.hashcurrent.next = Block(data, previous_hash)
For this, we create a loop that assigns the block data for the current node. print_blockchain prints the block data.
def print_blockchain(self):if self.head == None:print("The blockchain is empty")returnelse:current = self.headwhile current:print("Timestamp:", current.timestamp)print("Data:", current.data)print("Hash:", current.hash)print("Previous hash:", current.previous_hash)print("--------------->")current = current.next
bitcoin = Blockchain()bitcoin.add_block("block 1")bitcoin.add_block("block 2")bitcoin.add_block("block 3")bitcoin.print_blockchain()
In the above snippet, we create a new blockchain, then add some new blocks to it.
From this, we print out the blocks that we added.
import hashlibfrom datetime import datetimeclass Block:def __init__(self, data, previous_hash):self.timestamp = datetime.now()self.data = dataself.previous_hash = previous_hashself.hash = self.calc_hash()self.next = Nonedef calc_hash(self):# Include the block data in the hash calculationhash_str = "{}{}{}".format(self.timestamp, self.data, self.previous_hash).encode('utf-8')return hashlib.sha256(hash_str).hexdigest()class Blockchain:def __init__(self):self.head = Noneself.next = Nonedef add_block(self, data):if self.head == None:self.head = Block(data,0)else:current = self.head# loop to the last node of the linkedlistwhile current.next:current = current.next# stores the previous has for the next blockprevious_hash = current.hashcurrent.next = Block(data, previous_hash)def print_blockchain(self):if self.head == None:print("The blockchain is empty")returnelse:current = self.headwhile current:print("Timestamp:", current.timestamp)print("Data:", current.data)print("Hash:", current.hash)print("Previous hash:", current.previous_hash)print("--------------->")current = current.nextbitcoin = Blockchain()bitcoin.add_block("block 1")bitcoin.add_block("block 2")bitcoin.add_block("block 3")bitcoin.print_blockchain()