Make it possible to turn off automatic txout ordering

electrum/gui/qt/confirm_tx_dialog.py

@@ -414,6 +414,7 @@ def add_cv_action(configvar: 'ConfigVarWithConfig', action: Callable[[], None]):
         add_cv_action(self.config.cv.WALLET_MERGE_DUPLICATE_OUTPUTS, self.toggle_merge_duplicate_outputs)
         add_cv_action(self.config.cv.WALLET_SPEND_CONFIRMED_ONLY, self.toggle_confirmed_only)
         add_cv_action(self.config.cv.WALLET_COIN_CHOOSER_OUTPUT_ROUNDING, self.toggle_output_rounding)
+        add_cv_action(self.config.cv.WALLET_SORT_TX_OUTPUTS, self.toggle_sort_outputs)
         self.pref_button = QToolButton()
         self.pref_button.setIcon(read_QIcon("preferences.png"))
         self.pref_button.setMenu(self.pref_menu)
@@ -467,6 +468,11 @@ def toggle_confirmed_only(self):
         self.config.WALLET_SPEND_CONFIRMED_ONLY = b
         self.trigger_update()
 
+    def toggle_sort_outputs(self):
+        b = not self.config.WALLET_SORT_TX_OUTPUTS
+        self.config.WALLET_SORT_TX_OUTPUTS = b
+        self.trigger_update()
+
     def toggle_io_visibility(self):
         b = not self.config.GUI_QT_TX_EDITOR_SHOW_IO
         self.config.GUI_QT_TX_EDITOR_SHOW_IO = b

electrum/simple_config.py

@@ -991,6 +991,18 @@ def _default_swapserver_url(self) -> str:
         short_desc=lambda: _('Send change to Lightning'),
         long_desc=lambda: _('If possible, send the change of this transaction to your channels, with a submarine swap'),
     )
+    # TODO: once randomizing transaction outputs is implemented, replace the language here to randomize
+    WALLET_SORT_TX_OUTPUTS = ConfigVar(
+        'sort_tx_outputs', default=True, type_=bool,
+        short_desc=lambda: _('Sort transaction outputs (BIP-69)'),
+        long_desc=lambda: _("""Transaction outputs can be arbitrarily sorted, and transfers are still going to work.
+
+This means that from the ordering, one could deduce the client that was used to generate the transaction.
+
+By having a normalized order for the outputs of a transaction, the BIP-69 standard makes this fingerprinting impossible.
+
+This option is enabled by default, as it increases privacy, and it only should be turned off, if the generated transaction has to have a specific output ordering."""),
+    )
 
     FX_USE_EXCHANGE_RATE = ConfigVar('use_exchange_rate', default=False, type_=bool)
     FX_CURRENCY = ConfigVar('currency', default='EUR', type_=str)

electrum/wallet.py

@@ -1933,7 +1933,7 @@ def fee_estimator(size: Union[int, float, Decimal]) -> int:
 
             (x,i) = i_max[-1]
             outputs[i].value += (amount - distr_amount)
-            tx = PartialTransaction.from_io(list(coins), list(outputs))
+            tx = PartialTransaction.from_io(list(coins), list(outputs), BIP69_sort = self.config.WALLET_SORT_TX_OUTPUTS)
 
         # Timelock tx to current height.
         tx.locktime = get_locktime_for_new_transaction(self.network)