141 lines
5.1 KiB
Python
141 lines
5.1 KiB
Python
from dataclasses import dataclass
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from cryptography.hazmat.primitives.asymmetric.ed25519 import Ed25519PrivateKey, Ed25519PublicKey
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from cryptography.exceptions import InvalidSignature
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import hashlib
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import time
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@dataclass
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class Transaction:
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id: int
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sender: bytes
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receiver: bytes
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amount: int
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transaction_fee: int
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signature: bytes
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def is_valid(self):
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sender_pubkey = Ed25519PublicKey.from_public_bytes(self.sender)
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msg = self.id.to_bytes(4, "big") + \
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self.sender + \
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self.receiver + \
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self.amount.to_bytes(8, "big") + \
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self.transaction_fee(8, "big")
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try:
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sender_pubkey.verify(self.signature, msg)
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except InvalidSignature:
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return False
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return self.amount >= 1
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def is_valid_after_block(self, block):
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if (self.sender, self.id) in block.used_transaction_ids:
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return False
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balance = block.balances.get(self.sender)
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if balance is None:
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return False
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return balance >= self.amount + self.transaction_fee
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def get_transaction_raw(self):
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return self.id.to_bytes(4, "big") + \
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self.sender + \
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self.receiver + \
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self.amount.to_bytes(8, "big") + \
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self.transaction_fee.to_bytes(8, "big") + \
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self.signature
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@dataclass
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class Block:
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nonce: int
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timestamp: int
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previous_hash: bytes
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message: bytes
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difficulty_sum: int
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miner_pubkey: bytes
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transaction: Transaction
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balances: dict
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# (sender_pubkey, id) tuples
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used_transaction_ids: set
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valid: bool
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def validate(self, blockchain):
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if self.transaction is not None:
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if not self.transaction.is_valid():
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return False
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if self.previous_hash != 32 * b"\0":
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prev_block = blockchain.get_block(self.previous_hash)
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if not prev_block.valid:
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return False
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if self.timestamp <= prev_block.timestamp:
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return False
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if self.timestamp > time.time():
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return False
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if not self.transaction.is_valid_after_block(prev_block):
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return False
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elif self.transaction is not None:
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return False
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B_1_difficulty_sum, B_1_timestamp = self.get_difficulty_info(1, blockchain)
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B_10_difficulty_sum, B_10_timestamp = self.get_difficulty_info(10, blockchain)
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D = B_1_difficulty_sum - B_10_difficulty_sum
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T = self.timestamp - B_10_timestamp
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calculated_difficulty = D * 3000 // 9 // T
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block_difficulty = max(calculated_difficulty, 2**28)
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if B_1_difficulty_sum + block_difficulty != self.difficulty_sum:
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return False
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block_raw = self.get_block_raw()
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block_hash = hashlib.sha256(block_raw).digest()
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self.valid = int.from_bytes(block_hash, "big") * block_difficulty < 2**256
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if self.valid:
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self.calculate_balances(prev_block)
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self.calculate_used_transaction_ids(prev_block)
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return self.valid
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def calculate_balances(self, prev_block):
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if prev_block is None:
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self.balances = {
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self.miner_pubkey: 100,
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}
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return
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balances = prev_block.balances.copy()
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balances.setdefault(self.miner_pubkey, 0)
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balances[miner_pubkey] += 100
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t = self.transaction
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if t is not None:
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balances[miner_pubkey] += t.transaction_fee
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balances[t.sender] -= (t.amount + t.transaction_fee)
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balances[t.receiver] += t.amount
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self.balances = balances
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def calculate_used_transaction_ids(self, prev_block):
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if prev_block is None:
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self.used_transaction_ids = set()
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return
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used_transaction_ids = prev_block.used_transaction_ids.copy()
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t = self.transaction
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if t is not None:
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used_transaction_ids.add((t.sender, t.id))
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self.used_transaction_ids = used_transaction_ids
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def get_difficulty_info(self, steps, blockchain):
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if steps == 0:
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return self.difficulty_sum, self.timestamp
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if self.previous_hash == 32 * b"\0":
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difficulty_sum = 2**29 - steps * 2**28
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timestamp = self.timestamp - steps * 300
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return difficulty_sum, timestamp
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else:
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previous_block = blockchain.get_block(self.previous_hash)
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return previous_block.get_difficulty_info(steps-1, blockchain)
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def get_block_raw(self):
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if self.transaction is None:
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transaction = 148 * b"\0"
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else:
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transaction = self.transaction.get_transaction_raw()
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return self.nonce.to_bytes(8, "big") + \
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self.timestamp.to_bytes(8, "big") + \
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self.previous_hash + \
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self.message + \
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self.difficulty_sum.to_bytes(32, "big") + \
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self.miner_pubkey + \
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transaction
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class Blockchain:
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def __init__(self):
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# maps block hashes to block instances
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self.__block_map = {}
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def get_block(self, hash):
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return self.__block_map.get(hash)
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