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Update pow_algorithm.py

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Anurag Singh 2024-10-03 15:39:44 +05:30 committed by GitHub
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1 changed files with 40 additions and 42 deletions
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blockchain/pow_algorithm.py
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@ -1,17 +1,14 @@
"""
# Title: Proof of Work Algorithm for Blockchain
## Algorithm Statement:
The algorithm implements the Proof of Work (PoW) consensus mechanism used in
blockchain to validate blocks. PoW ensures participants (miners) perform a
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.
"""
# The algorithm implements the Proof of Work (PoW) consensus mechanism used in
# blockchain to validate blocks. PoW ensures participants (miners) perform a
# 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.
import hashlib
import time
class Block:
def __init__(
self,
@ -19,7 +16,7 @@ class Block:
previous_hash: str,
transactions: str,
timestamp: float,
difficulty: int,
difficulty: int
) -> None:
"""
Initializes a Block object with the specified parameters.
@ -28,7 +25,8 @@ class Block:
- index (int): The index of the block in the blockchain.
- previous_hash (str): The hash of the previous block.
- transactions (str): The list of transactions in the block.
- timestamp (float): The time when the block was created (in Unix timestamp format).
- timestamp (float): The time when the block was created
(in Unix timestamp format).
- difficulty (int): The difficulty level for mining this block.
"""
self.index = index
@ -42,9 +40,9 @@ class Block:
def compute_hash(self) -> str:
"""
Generates the hash of the block content.
Combines index, previous hash, transactions, timestamp, and nonce into a string,
which is then hashed using SHA-256.
Combines index, previous hash, transactions, timestamp, and nonce into
a string, which is then hashed using SHA-256.
Returns:
- str: The hash of the block.
"""
@ -57,21 +55,19 @@ class Block:
def mine_block(self) -> None:
"""
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 level.
A valid hash has the required number of leading zeros based on the
difficulty level.
Returns:
- None
"""
target = (
"0" * self.difficulty
) # Target hash should start with 'difficulty' zeros
while self.hash[: self.difficulty] != target:
target = '0' * self.difficulty # Target hash should start with 'difficulty' zeros
while self.hash[:self.difficulty] != target:
self.nonce += 1
self.hash = self.compute_hash()
print(f"Block mined with nonce {self.nonce}, hash: {self.hash}")
class Blockchain:
def __init__(self, difficulty: int) -> None:
"""
@ -79,18 +75,18 @@ class Blockchain:
Parameters:
- difficulty (int): The difficulty level for mining blocks in this blockchain.
Returns:
- None
"""
self.chain = []
self.chain: list[Block] = [] # Adding type hint for the list of blocks
self.difficulty = difficulty
self.create_genesis_block()
def create_genesis_block(self) -> None:
"""
Creates the first block in the blockchain (the Genesis block).
Returns:
- None
"""
@ -104,24 +100,21 @@ class Blockchain:
Parameters:
- transactions (str): The list of transactions to be added in the new block.
Returns:
- None
"""
previous_block = self.chain[-1]
new_block = Block(
len(self.chain),
previous_block.hash,
transactions,
time.time(),
self.difficulty,
len(self.chain), previous_block.hash, transactions, time.time(),
self.difficulty
)
new_block.mine_block()
self.chain.append(new_block)
def is_chain_valid(self) -> bool:
"""
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.
Returns:
@ -141,37 +134,42 @@ class Blockchain:
return True
# Test cases
## Test Case 1: Blockchain Initialization and Genesis Block
# This test verifies if the blockchain is correctly initialized with a Genesis block
# and if the block is successfully mined.
def test_blockchain() -> None:
"""
Test cases for the Blockchain proof of work algorithm.
Returns:
- None
"""
# Create blockchain with difficulty level of 4 (hash should start with 4 zeros)
blockchain = Blockchain(difficulty=4)
# Add new blocks
## Test Case 2: Add a block and verify the block is mined
# This test adds a new block with transactions and ensures it's mined according
# to the proof of work mechanism.
blockchain.add_block("Transaction 1: Alice pays Bob 5 BTC")
blockchain.add_block("Transaction 2: Bob pays Charlie 3 BTC")
# Verify the integrity of the blockchain
## Test Case 3: Verify blockchain integrity
# This test checks that the blockchain remains valid after adding new blocks
assert blockchain.is_chain_valid(), "Blockchain should be valid"
# Tamper with the blockchain and check validation
blockchain.chain[
1
].transactions = "Transaction 1: Alice pays Bob 50 BTC" # Tampering
assert (
not blockchain.is_chain_valid()
), "Blockchain should be invalid due to tampering"
## Test Case 4: Tampering with the blockchain
# This test simulates tampering with the blockchain and checks that the validation
# correctly detects the tampering.
blockchain.chain[1].transactions = "Transaction 1: Alice pays Bob 50 BTC" # Tampering
assert not blockchain.is_chain_valid(), "Blockchain should be invalid due to tampering"
## Test Case 5: Correct blockchain validation
# This test checks if the blockchain becomes invalid after tampering and verifies
# if the PoW still holds after tampering is done.
print("All test cases passed.")
if __name__ == "__main__":
test_blockchain()