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Add: blockchain/simple_proof_of_work.py #14237

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Add: blockchain/simple_proof_of_work.py #14237

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62 changes: 62 additions & 0 deletions blockchain/simple_proof_of_work.py
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"""
Proof of Work (PoW) implementation.
This algorithm is used in blockchain technology
to reach consensus and secure the network
"""

import hashlib


def proof_of_work(
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@algorithms-keeper algorithms-keeper bot Feb 2, 2026

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As there is no test file in this pull request nor any test function or class in the file blockchain/simple_proof_of_work.py, please provide doctest for the function proof_of_work

block_number: int, transactions: str, previous_hash: str, difficulty: int
) -> tuple[int, str]:
"""
Finds a nonce such that the SHA-256 hash of the block starts with
a specific number of zeros (difficulty).

>>> proof_of_work(1, "test", "abc", 1)[1].startswith("0")
True
>>> # Consistency check: same input must produce same output
>>> res1 = proof_of_work(1, "data", "hash", 2)
>>> res2 = proof_of_work(1, "data", "hash", 2)
>>> res1 == res2
True
>>> # Difficulty 0 should return nonce 0 immediately
>>> proof_of_work(1, "data", "hash", 0)[0]
0
"""
if difficulty < 0:
raise ValueError("difficulty must be a non-negative integer")

prefix = "0" * difficulty
nonce = 0

while True:
# Create a single string representing all block data
text = f"{block_number}{transactions}{previous_hash}{nonce}"

# Calculate the SHA-256 hash
current_hash = hashlib.sha256(text.encode()).hexdigest()

# Check if the hash meets the difficulty requirement
if current_hash.startswith(prefix):
return nonce, current_hash

nonce += 1


if __name__ == "__main__":
import doctest

doctest.testmod()

# Example usage:
example_tx = "Alice sends 1 BTC to Bob"
prev_h = "00000abcdef1234567890"
diff = 4

print(f"Mining block... (Difficulty: {diff})")
nonce, hash_found = proof_of_work(1, example_tx, prev_h, diff)

print(f"Success! Nonce: {nonce}")
print(f"Hash: {hash_found}")