tAdd coin chooser to try and minimize loss of privacy. - electrum - Electrum Bitcoin wallet
HTML git clone https://git.parazyd.org/electrum
DIR Log
DIR Files
DIR Refs
DIR Submodules
---
DIR commit 75b3ecee491ea1962a0be043eaceec9e8348a676
DIR parent de964f40336a51dc5e1e9c149c55fc37e8608393
HTML Author: Neil Booth <kyuupichan@gmail.com>
Date: Sun, 29 Nov 2015 23:19:13 +0900
Add coin chooser to try and minimize loss of privacy.
Diffstat:
M gui/qt/main_window.py | 17 ++++++++++++++++-
M lib/__init__.py | 4 ++--
M lib/coinchooser.py | 144 ++++++++++++++++++++++++++-----
M lib/wallet.py | 31 ++++++++++++++++++++++++++-----
4 files changed, 167 insertions(+), 29 deletions(-)
---
DIR diff --git a/gui/qt/main_window.py b/gui/qt/main_window.py
t@@ -43,7 +43,7 @@ from electrum.util import PrintError, NotEnoughFunds, StoreDict
from electrum import Transaction
from electrum import mnemonic
from electrum import util, bitcoin, commands, Wallet
-from electrum import SimpleConfig, Wallet, WalletStorage
+from electrum import SimpleConfig, COIN_CHOOSERS, WalletStorage
from electrum import Imported_Wallet
from electrum import paymentrequest
t@@ -2593,6 +2593,21 @@ class ElectrumWindow(QMainWindow, PrintError):
nz.valueChanged.connect(on_nz)
gui_widgets.append((nz_label, nz))
+ choosers = sorted(COIN_CHOOSERS.keys())
+ chooser_name = self.wallet.coin_chooser_name(self.config)
+ msg = _('Choose coin (UTXO) selection method. The following are available:\n\n')
+ msg += '\n\n'.join(key + ": " + klass.__doc__
+ for key, klass in COIN_CHOOSERS.items())
+ chooser_label = HelpLabel(_('Coin selection') + ':', msg)
+ chooser_combo = QComboBox()
+ chooser_combo.addItems(choosers)
+ chooser_combo.setCurrentIndex(choosers.index(chooser_name))
+ def on_chooser(x):
+ chooser_name = choosers[chooser_combo.currentIndex()]
+ self.config.set_key('coin_chooser', chooser_name)
+ chooser_combo.currentIndexChanged.connect(on_chooser)
+ tx_widgets.append((chooser_label, chooser_combo))
+
msg = _('Fee per kilobyte of transaction.') + '\n' \
+ _('If you enable dynamic fees, this parameter will be used as upper bound.')
fee_label = HelpLabel(_('Transaction fee per kb') + ':', msg)
DIR diff --git a/lib/__init__.py b/lib/__init__.py
t@@ -1,7 +1,7 @@
from version import ELECTRUM_VERSION
from util import format_satoshis, print_msg, print_error, set_verbosity
-from wallet import Synchronizer, WalletStorage
-from wallet import Wallet, Imported_Wallet
+from wallet import Synchronizer, WalletStorage, Wallet, Imported_Wallet
+from coinchooser import COIN_CHOOSERS
from network import Network, DEFAULT_SERVERS, DEFAULT_PORTS, pick_random_server
from interface import Connection, Interface
from simple_config import SimpleConfig, get_config, set_config
DIR diff --git a/lib/coinchooser.py b/lib/coinchooser.py
t@@ -17,14 +17,19 @@
# along with this program. If not, see <http://www.gnu.org/licenses/>.
from collections import defaultdict, namedtuple
+from random import shuffle
-from util import NotEnoughFunds, PrintError, profiler
+from bitcoin import COIN
from transaction import Transaction
+from util import NotEnoughFunds, PrintError, profiler
Bucket = namedtuple('Bucket', ['desc', 'size', 'value', 'coins'])
class CoinChooserBase(PrintError):
+ def keys(self, coins):
+ raise NotImplementedError
+
def bucketize_coins(self, coins):
keys = self.keys(coins)
buckets = defaultdict(list)
t@@ -39,55 +44,66 @@ class CoinChooserBase(PrintError):
return map(make_Bucket, buckets.keys(), buckets.values())
+ def penalty_func(self, tx):
+ def penalty(candidate):
+ return 0
+ return penalty
+
+ def add_change(self, tx, change_addrs, fee_estimator, dust_threshold):
+ # How much is left if we add 1 change output?
+ change_amount = tx.get_fee() - fee_estimator(1)
+
+ # If change is above dust threshold after accounting for the
+ # size of the change output, add it to the transaction.
+ if change_amount > dust_threshold:
+ tx.outputs.append(('address', change_addrs[0], change_amount))
+ self.print_error('change', change_amount)
+ elif change_amount:
+ self.print_error('not keeping dust', change_amount)
+
def make_tx(self, coins, outputs, change_addrs, fee_estimator,
dust_threshold):
'''Select unspent coins to spend to pay outputs. If the change is
greater than dust_threshold (after adding the change output to
the transaction) it is kept, otherwise none is sent and it is
added to the transaction fee.'''
- output_total = sum(map(lambda x: x[2], outputs))
+ # Copy the ouputs so when adding change we don't modify "outputs"
+ tx = Transaction.from_io([], outputs[:])
# Size of the transaction with no inputs and no change
- tx = Transaction.from_io([], outputs)
base_size = tx.estimated_size()
# Returns fee given input size
fee = lambda input_size: fee_estimator(base_size + input_size)
# Collect the coins into buckets, choose a subset of the buckets
buckets = self.bucketize_coins(coins)
- buckets = self.choose_buckets(buckets, output_total, fee)
+ buckets = self.choose_buckets(buckets, tx.output_value(), fee,
+ self.penalty_func(tx))
tx.inputs = [coin for b in buckets for coin in b.coins]
- input_total = sum(bucket.value for bucket in buckets)
tx_size = base_size + sum(bucket.size for bucket in buckets)
- # If change is above dust threshold after accounting for the
- # size of the change output, add it to the transaction.
- # Pay to bitcoin address serializes as 34 bytes
- change_size = 34
- fee = fee_estimator(tx_size + change_size)
- change_amount = input_total - (output_total + fee)
- if change_amount > dust_threshold:
- tx.outputs.append(('address', change_addrs[0], change_amount))
- self.print_error('change', change_amount)
- elif change_amount:
- self.print_error('not keeping dust', change_amount)
+ # This takes a count of change outputs and returns a tx fee;
+ # each pay-to-bitcoin-address output serializes as 34 bytes
+ fee = lambda count: fee_estimator(tx_size + count * 34)
+ self.add_change(tx, change_addrs, fee, dust_threshold)
self.print_error("using %d inputs" % len(tx.inputs))
self.print_error("using buckets:", [bucket.desc for bucket in buckets])
return tx
-class CoinChooser(CoinChooserBase):
- '''The original electrum algorithm. Chooses coins starting with the
- oldest that are sufficient to cover the spent amount, and then
- removes any not needed starting with the smallest in value.'''
+class CoinChooserClassic(CoinChooserBase):
+ '''
+ The classic electrum algorithm. Chooses coins starting with
+ the oldest that are sufficient to cover the spent amount, and
+ then removes any unneeded starting with the smallest in value.'''
def keys(self, coins):
return [coin['prevout_hash'] + ':' + str(coin['prevout_n'])
for coin in coins]
- def choose_buckets(self, buckets, spent_amount, fee):
+ def choose_buckets(self, buckets, spent_amount, fee, penalty_func):
'''Spend the oldest buckets first.'''
# Unconfirmed coins are young, not old
adj_height = lambda height: 99999999 if height == 0 else height
t@@ -113,3 +129,89 @@ class CoinChooser(CoinChooserBase):
dropped.append(bucket)
return [bucket for bucket in selected if bucket not in dropped]
+
+class CoinChooserRandom(CoinChooserBase):
+
+ def bucket_candidates(self, buckets, sufficient_funds):
+ '''Returns a list of bucket sets.'''
+ candidates = set()
+
+ # Add all singletons
+ for n, bucket in enumerate(buckets):
+ if sufficient_funds([bucket]):
+ candidates.add((n, ))
+
+ # And now some random ones
+ attempts = min(100, (len(buckets) - 1) * 10 + 1)
+ permutation = range(len(buckets))
+ for i in range(attempts):
+ # Get a random permutation of the buckets, and
+ # incrementally combine buckets until sufficient
+ shuffle(permutation)
+ bkts = []
+ for count, index in enumerate(permutation):
+ bkts.append(buckets[index])
+ if sufficient_funds(bkts):
+ candidates.add(tuple(sorted(permutation[:count + 1])))
+ break
+ else:
+ raise NotEnoughFunds()
+
+ return [[buckets[n] for n in candidate] for candidate in candidates]
+
+ def choose_buckets(self, buckets, spent_amount, fee, penalty_func):
+
+ def sufficient(buckets):
+ '''Given a set of buckets, return True if it has enough
+ value to pay for the transaction'''
+ total_input = sum(bucket.value for bucket in buckets)
+ total_size = sum(bucket.size for bucket in buckets)
+ return total_input >= spent_amount + fee(total_size)
+
+ candidates = self.bucket_candidates(buckets, sufficient)
+ penalties = [penalty_func(cand) for cand in candidates]
+ winner = candidates[penalties.index(min(penalties))]
+ self.print_error("Bucket sets:", len(buckets))
+ self.print_error("Winning penalty:", min(penalties))
+ return winner
+
+class CoinChooserPrivacy(CoinChooserRandom):
+ '''
+ Attempts to better preserve user privacy. First, if any coin is
+ spent from a user address, all coins are. Compared to spending
+ from other addresses to make up an amount, this reduces
+ information leakage about sender holdings. It also helps to
+ reduce blockchain UTXO bloat, and reduce future privacy loss
+ that would come from reusing that address' remaining UTXOs.
+ Second, it penalizes change that is quite different to the sent
+ amount. Third, it penalizes change that is too big.'''
+
+ def keys(self, coins):
+ return [coin['address'] for coin in coins]
+
+ def penalty_func(self, buckets, tx):
+ '''Returns a penalty for a candidate set of buckets.'''
+ raise NotImplementedError
+
+ def penalty_func(self, tx):
+ min_change = min(o[2] for o in tx.outputs) * 0.75
+ max_change = max(o[2] for o in tx.outputs) * 1.33
+ spent_amount = sum(o[2] for o in tx.outputs)
+
+ def penalty(buckets):
+ badness = len(buckets) - 1
+ total_input = sum(bucket.value for bucket in buckets)
+ change = float(total_input - spent_amount)
+ # Penalize change not roughly in output range
+ if change < min_change:
+ badness += (min_change - change) / (min_change + 10000)
+ elif change > max_change:
+ badness += (change - max_change) / (max_change + 10000)
+ # Penalize large change; 5 BTC excess ~= using 1 more input
+ badness += change / (COIN * 5)
+ return badness
+
+ return penalty
+
+COIN_CHOOSERS = {'Classic': CoinChooserClassic,
+ 'Privacy': CoinChooserPrivacy}
DIR diff --git a/lib/wallet.py b/lib/wallet.py
t@@ -35,7 +35,7 @@ from version import *
from transaction import Transaction
from plugins import run_hook
import bitcoin
-from coinchooser import CoinChooser
+from coinchooser import COIN_CHOOSERS
from synchronizer import Synchronizer
from verifier import SPV
from mnemonic import Mnemonic
t@@ -45,7 +45,6 @@ import paymentrequest
# internal ID for imported account
IMPORTED_ACCOUNT = '/x'
-
class WalletStorage(PrintError):
def __init__(self, path):
t@@ -156,7 +155,6 @@ class Abstract_Wallet(PrintError):
self.network = None
self.electrum_version = ELECTRUM_VERSION
self.gap_limit_for_change = 6 # constant
- self.coin_chooser = CoinChooser()
# saved fields
self.seed_version = storage.get('seed_version', NEW_SEED_VERSION)
self.use_change = storage.get('use_change',True)
t@@ -195,6 +193,7 @@ class Abstract_Wallet(PrintError):
self.lock = threading.Lock()
self.transaction_lock = threading.Lock()
self.tx_event = threading.Event()
+ self.tx_cache = (None, None, None, None, None)
self.check_history()
t@@ -205,6 +204,7 @@ class Abstract_Wallet(PrintError):
def diagnostic_name(self):
return self.basename()
+
@profiler
def load_transactions(self):
self.txi = self.storage.get('txi', {})
t@@ -896,6 +896,16 @@ class Abstract_Wallet(PrintError):
# this method can be overloaded
return tx.get_fee()
+ def coin_chooser_name(self, config):
+ kind = config.get('coin_chooser')
+ if not kind in COIN_CHOOSERS:
+ kind = 'Classic'
+ return kind
+
+ def coin_chooser(self, config):
+ klass = COIN_CHOOSERS[self.coin_chooser_name(config)]
+ return klass()
+
def make_unsigned_transaction(self, coins, outputs, config, fixed_fee=None, change_addr=None):
# check outputs
for type, data, value in outputs:
t@@ -934,13 +944,24 @@ class Abstract_Wallet(PrintError):
# Change <= dust threshold is added to the tx fee
dust_threshold = 182 * 3 * MIN_RELAY_TX_FEE / 1000
+ # Check cache to see if we just calculated this. If prior
+ # calculated a fee and this fixes it to the same, return same
+ # answer, to avoid random coin selection changing the answer
+ if self.tx_cache[:4] == (outputs, coins, change_addrs, dust_threshold):
+ tx = self.tx_cache[4]
+ if tx.get_fee() == fee_estimator(tx.estimated_size()):
+ return tx
+
# Let the coin chooser select the coins to spend
- tx = self.coin_chooser.make_tx(coins, outputs, change_addrs,
- fee_estimator, dust_threshold)
+ coin_chooser = self.coin_chooser(config)
+ tx = coin_chooser.make_tx(coins, outputs, change_addrs,
+ fee_estimator, dust_threshold)
# Sort the inputs and outputs deterministically
tx.BIP_LI01_sort()
+ self.tx_cache = (outputs, coins, change_addrs, dust_threshold, tx)
+
run_hook('make_unsigned_transaction', self, tx)
return tx