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commit 66cd40e387
1 changed files with 27 additions and 11 deletions
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38
blockchain/pow_algorithm.py
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@ -2,15 +2,16 @@
# Title: Proof of Work Algorithm for Blockchain # Title: Proof of Work Algorithm for Blockchain
## Algorithm Statement: ## Algorithm Statement:
The algorithm implements the Proof of Work (PoW) consensus mechanism used in The algorithm implements the Proof of Work (PoW) consensus mechanism used in
blockchain to validate blocks. PoW ensures participants (miners) perform a blockchain to validate blocks. PoW ensures participants (miners) perform a
computational task to create a valid block and add it to the blockchain. The computational task to create a valid block and add it to the blockchain. The
difficulty is defined by the number of leading zeros required in the block hash. difficulty is defined by the number of leading zeros required in the block hash.
""" """
import hashlib import hashlib
import time import time
class Block: class Block:
def __init__(self, index, previous_hash, transactions, timestamp, difficulty): def __init__(self, index, previous_hash, transactions, timestamp, difficulty):
self.index = index self.index = index
@ -36,16 +37,19 @@ class Block:
def mine_block(self): def mine_block(self):
""" """
Performs Proof of Work by adjusting the nonce until a valid hash is found. Performs Proof of Work by adjusting the nonce until a valid hash is found.
A valid hash has the required number of leading zeros based on the difficulty A valid hash has the required number of leading zeros based on the difficulty
level. level.
""" """
target = '0' * self.difficulty # Target hash should start with 'difficulty' zeros target = (
while self.hash[:self.difficulty] != target: "0" * self.difficulty
) # Target hash should start with 'difficulty' zeros
while self.hash[: self.difficulty] != target:
self.nonce += 1 self.nonce += 1
self.hash = self.compute_hash() self.hash = self.compute_hash()
print(f"Block mined with nonce {self.nonce}, hash: {self.hash}") print(f"Block mined with nonce {self.nonce}, hash: {self.hash}")
class Blockchain: class Blockchain:
def __init__(self, difficulty): def __init__(self, difficulty):
self.chain = [] self.chain = []
@ -65,14 +69,19 @@ class Blockchain:
Adds a new block to the blockchain after performing Proof of Work. Adds a new block to the blockchain after performing Proof of Work.
""" """
previous_block = self.chain[-1] previous_block = self.chain[-1]
new_block = Block(len(self.chain), previous_block.hash, transactions, time.time(), new_block = Block(
self.difficulty) len(self.chain),
previous_block.hash,
transactions,
time.time(),
self.difficulty,
)
new_block.mine_block() new_block.mine_block()
self.chain.append(new_block) self.chain.append(new_block)
def is_chain_valid(self): def is_chain_valid(self):
""" """
Verifies the integrity of the blockchain by ensuring each block's previous Verifies the integrity of the blockchain by ensuring each block's previous
hash matches and that all blocks meet the Proof of Work requirement. hash matches and that all blocks meet the Proof of Work requirement.
""" """
for i in range(1, len(self.chain)): for i in range(1, len(self.chain)):
@ -89,8 +98,10 @@ class Blockchain:
return True return True
# Test cases # Test cases
def test_blockchain(): def test_blockchain():
""" """
Test cases for the Blockchain proof of work algorithm. Test cases for the Blockchain proof of work algorithm.
@ -106,11 +117,16 @@ def test_blockchain():
assert blockchain.is_chain_valid(), "Blockchain should be valid" assert blockchain.is_chain_valid(), "Blockchain should be valid"
# Tamper with the blockchain and check validation # Tamper with the blockchain and check validation
blockchain.chain[1].transactions = "Transaction 1: Alice pays Bob 50 BTC" # Tampering blockchain.chain[
assert not blockchain.is_chain_valid(), "Blockchain should be invalid due to tampering" 1
].transactions = "Transaction 1: Alice pays Bob 50 BTC" # Tampering
assert (
not blockchain.is_chain_valid()
), "Blockchain should be invalid due to tampering"
print("All test cases passed.") print("All test cases passed.")
if __name__ == "__main__": if __name__ == "__main__":
test_blockchain() test_blockchain()