mirror of
https://github.com/aljazceru/nutshell.git
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264 lines
11 KiB
Python
264 lines
11 KiB
Python
"""
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Implementation of https://gist.github.com/phyro/935badc682057f418842c72961cf096c
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"""
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import hashlib
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from core.secp import PrivateKey, PublicKey
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from typing import List, Set
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from core.base import Proof, BlindedMessage, BlindedSignature
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import core.b_dhke as b_dhke
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from core.base import Invoice
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from core.db import Database
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from core.settings import MAX_ORDER, LIGHTNING
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from core.helpers import fee_reserve
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from core.split import amount_split
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from lightning import WALLET
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from mint.crud import (
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get_lightning_invoice,
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get_proofs_used,
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invalidate_proof,
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store_lightning_invoice,
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store_promise,
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update_lightning_invoice,
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)
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class Ledger:
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def __init__(self, secret_key: str, db: str):
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self.proofs_used: Set[str] = set()
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self.master_key: str = secret_key
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self.keys: List[PrivateKey] = self._derive_keys(self.master_key)
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self.pub_keys: List[PublicKey] = self._derive_pubkeys(self.keys)
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self.db: Database = Database("mint", db)
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async def load_used_proofs(self):
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self.proofs_used = set(await get_proofs_used(db=self.db))
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@staticmethod
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def _derive_keys(master_key: str):
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"""Deterministic derivation of keys for 2^n values."""
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return {
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2
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** i: PrivateKey(
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hashlib.sha256((str(master_key) + str(i)).encode("utf-8"))
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.hexdigest()
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.encode("utf-8")[:32],
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raw=True,
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)
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for i in range(MAX_ORDER)
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}
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@staticmethod
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def _derive_pubkeys(keys: List[PrivateKey]):
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return {amt: keys[amt].pubkey for amt in [2**i for i in range(MAX_ORDER)]}
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async def _generate_promises(self, amounts: List[int], B_s: List[str]):
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"""Generates promises that sum to the given amount."""
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return [
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await self._generate_promise(amount, PublicKey(bytes.fromhex(B_), raw=True))
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for (amount, B_) in zip(amounts, B_s)
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]
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async def _generate_promise(self, amount: int, B_: PublicKey):
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"""Generates a promise for given amount and returns a pair (amount, C')."""
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secret_key = self.keys[amount] # Get the correct key
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C_ = b_dhke.step2_alice(B_, secret_key)
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await store_promise(
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amount, B_=B_.serialize().hex(), C_=C_.serialize().hex(), db=self.db
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)
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return BlindedSignature(amount=amount, C_=C_.serialize().hex())
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def _check_spendable(self, proof: Proof):
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"""Checks whether the proof was already spent."""
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return not proof.secret in self.proofs_used
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def _verify_proof(self, proof: Proof):
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"""Verifies that the proof of promise was issued by this ledger."""
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if not self._check_spendable(proof):
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raise Exception(f"tokens already spent. Secret: {proof.secret}")
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secret_key = self.keys[proof.amount] # Get the correct key to check against
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C = PublicKey(bytes.fromhex(proof.C), raw=True)
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return b_dhke.verify(secret_key, C, proof.secret)
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def _verify_outputs(
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self, total: int, amount: int, output_data: List[BlindedMessage]
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):
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"""Verifies the expected split was correctly computed"""
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fst_amt, snd_amt = total - amount, amount # we have two amounts to split to
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fst_outputs = amount_split(fst_amt)
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snd_outputs = amount_split(snd_amt)
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expected = fst_outputs + snd_outputs
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given = [o.amount for o in output_data]
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return given == expected
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def _verify_no_duplicates(
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self, proofs: List[Proof], output_data: List[BlindedMessage]
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):
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secrets = [p.secret for p in proofs]
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if len(secrets) != len(list(set(secrets))):
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return False
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B_s = [od.B_ for od in output_data]
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if len(B_s) != len(list(set(B_s))):
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return False
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return True
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def _verify_split_amount(self, amount: int):
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"""Split amount like output amount can't be negative or too big."""
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try:
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self._verify_amount(amount)
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except:
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# For better error message
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raise Exception("invalid split amount: " + str(amount))
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def _verify_amount(self, amount: int):
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"""Any amount used should be a positive integer not larger than 2^MAX_ORDER."""
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valid = isinstance(amount, int) and amount > 0 and amount < 2**MAX_ORDER
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if not valid:
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raise Exception("invalid amount: " + str(amount))
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return amount
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def _verify_equation_balanced(
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self, proofs: List[Proof], outs: List[BlindedMessage]
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):
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"""Verify that Σoutputs - Σinputs = 0."""
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sum_inputs = sum(self._verify_amount(p.amount) for p in proofs)
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sum_outputs = sum(self._verify_amount(p.amount) for p in outs)
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assert sum_outputs - sum_inputs == 0
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def _get_output_split(self, amount: int):
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"""Given an amount returns a list of amounts returned e.g. 13 is [1, 4, 8]."""
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self._verify_amount(amount)
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bits_amt = bin(amount)[::-1][:-2]
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rv = []
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for (pos, bit) in enumerate(bits_amt):
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if bit == "1":
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rv.append(2**pos)
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return rv
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async def _request_lightning_invoice(self, amount: int):
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"""Returns an invoice from the Lightning backend."""
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error, balance = await WALLET.status()
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if error:
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raise Exception(f"Lightning wallet not responding: {error}")
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ok, checking_id, payment_request, error_message = await WALLET.create_invoice(
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amount, "cashu deposit"
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)
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return payment_request, checking_id
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async def _check_lightning_invoice(self, payment_hash: str):
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"""Checks with the Lightning backend whether an invoice with this payment_hash was paid."""
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invoice: Invoice = await get_lightning_invoice(payment_hash, db=self.db)
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if invoice.issued:
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raise Exception("tokens already issued for this invoice")
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status = await WALLET.get_invoice_status(payment_hash)
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if status.paid:
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await update_lightning_invoice(payment_hash, issued=True, db=self.db)
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return status.paid
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async def _pay_lightning_invoice(self, invoice: str, amount: int):
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"""Returns an invoice from the Lightning backend."""
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error, balance = await WALLET.status()
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if error:
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raise Exception(f"Lightning wallet not responding: {error}")
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ok, checking_id, fee_msat, preimage, error_message = await WALLET.pay_invoice(
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invoice, fee_limit_msat=fee_reserve(amount * 1000)
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)
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return ok, preimage
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async def _invalidate_proofs(self, proofs: List[Proof]):
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"""Adds secrets of proofs to the list of knwon secrets and stores them in the db."""
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# Mark proofs as used and prepare new promises
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proof_msgs = set([p.secret for p in proofs])
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self.proofs_used |= proof_msgs
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# store in db
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for p in proofs:
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await invalidate_proof(p, db=self.db)
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# Public methods
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def get_pubkeys(self):
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"""Returns public keys for possible amounts."""
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return {a: p.serialize().hex() for a, p in self.pub_keys.items()}
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async def request_mint(self, amount):
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"""Returns Lightning invoice and stores it in the db."""
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payment_request, checking_id = await self._request_lightning_invoice(amount)
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invoice = Invoice(
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amount=amount, pr=payment_request, hash=checking_id, issued=False
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)
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if not payment_request or not checking_id:
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raise Exception(f"Could not create Lightning invoice.")
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await store_lightning_invoice(invoice, db=self.db)
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return payment_request, checking_id
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async def mint(self, B_s: List[PublicKey], amounts: List[int], payment_hash=None):
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"""Mints a promise for coins for B_."""
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# check if lightning invoice was paid
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if LIGHTNING and (
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payment_hash and not await self._check_lightning_invoice(payment_hash)
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):
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raise Exception("Lightning invoice not paid yet.")
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for amount in amounts:
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if amount not in [2**i for i in range(MAX_ORDER)]:
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raise Exception(f"Can only mint amounts up to {2**MAX_ORDER}.")
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promises = [
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await self._generate_promise(amount, B_) for B_, amount in zip(B_s, amounts)
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]
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return promises
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async def melt(self, proofs: List[Proof], amount: int, invoice: str):
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"""Invalidates proofs and pays a Lightning invoice."""
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# if not LIGHTNING:
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total = sum([p["amount"] for p in proofs])
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# check that lightning fees are included
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assert total + fee_reserve(amount * 1000) >= amount, Exception(
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"provided proofs not enough for Lightning payment."
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)
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status, preimage = await self._pay_lightning_invoice(invoice, amount)
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if status == True:
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await self._invalidate_proofs(proofs)
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return status, preimage
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async def check_spendable(self, proofs: List[Proof]):
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"""Checks if all provided proofs are valid and still spendable (i.e. have not been spent)."""
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if not all([self._check_spendable(p) for p in proofs]):
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return False
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return True
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async def split(
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self, proofs: List[Proof], amount: int, output_data: List[BlindedMessage]
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):
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"""Consumes proofs and prepares new promises based on the amount split."""
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self._verify_split_amount(amount)
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# Verify proofs are valid
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if not all([self._verify_proof(p) for p in proofs]):
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return False
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total = sum([p.amount for p in proofs])
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if not self._verify_no_duplicates(proofs, output_data):
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raise Exception("duplicate proofs or promises")
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if amount > total:
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raise Exception("split amount is higher than the total sum")
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if not self._verify_outputs(total, amount, output_data):
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raise Exception("split of promises is not as expected")
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# Mark proofs as used and prepare new promises
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await self._invalidate_proofs(proofs)
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outs_fst = amount_split(total - amount)
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outs_snd = amount_split(amount)
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B_fst = [od.B_ for od in output_data[: len(outs_fst)]]
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B_snd = [od.B_ for od in output_data[len(outs_fst) :]]
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prom_fst, prom_snd = await self._generate_promises(
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outs_fst, B_fst
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), await self._generate_promises(outs_snd, B_snd)
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self._verify_equation_balanced(proofs, prom_fst + prom_snd)
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return prom_fst, prom_snd
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