Share cosigner via QR code (for Specter import)

src/App.js

@@ -24,6 +24,7 @@ import SendPsbtScreen from './screen/send-psbt';
 import SendConfirmScreen from './screen/send-confirm';
 import SendSuccessScreen from './screen/send-success';
 import SettingsScreen from './screen/settings';
+import CosignerExportScreen from './screen/cosigner-export';
 import EmailSetScreen from './screen/email-set';
 import EmailPinScreen from './screen/email-pin';
 import EmailVerifyScreen from './screen/email-verify';
@@ -35,6 +36,7 @@ const PinChangeStack = createStackNavigator();
 const PinCheckStack = createStackNavigator();
 const RestoreStack = createStackNavigator();
 const EmailSetStack = createStackNavigator();
+const CosignerExportStack = createStackNavigator();
 const MainStack = createBottomTabNavigator();
 const RootStack = createStackNavigator();
 
@@ -139,6 +141,21 @@ const PinChangeStackScreen = () => (
   </PinChangeStack.Navigator>
 );
 
+const CosignerExportStackScreen = () => (
+  <CosignerExportStack.Navigator>
+    <CosignerExportStack.Screen
+      name="CosignerExport"
+      component={CosignerExportScreen}
+      options={{
+        title: 'Export Cosigner',
+        headerLeft: () => (
+          <HeaderBackButton label="Settings" onPress={() => nav.goBack()} />
+        ),
+      }}
+    />
+  </CosignerExportStack.Navigator>
+);
+
 const PinCheckStackScreen = () => (
   <PinCheckStack.Navigator>
     <PinCheckStack.Screen
@@ -284,6 +301,11 @@ const App = () => (
         component={PinChangeStackScreen}
         options={{headerShown: false}}
       />
+      <RootStack.Screen
+        name="CosignerExport"
+        component={CosignerExportStackScreen}
+        options={{headerShown: false}}
+      />
     </RootStack.Navigator>
   </NavigationContainer>
 );

src/action/multisig.js

@@ -4,9 +4,54 @@ import RNFS from 'react-native-fs';
 import {MultisigHDWallet} from '@photon-sdk/photon-lib';
 
 import store from '../store';
+import * as nav from './nav';
 import * as alert from './alert';
 import {getWallet, getMultisigWallet, walletStore} from './wallet';
 
+const PATH = "m/48'/0'/0'/2'";
+
+//
+// Export Cosigner
+//
+
+function _loadCosignerExport() {
+  const mnemonic = walletStore.wallets[0].getSecret();
+  const msWallet = new MultisigHDWallet();
+  msWallet.setDerivationPath(PATH);
+  const xpub = MultisigHDWallet.seedToXpub(mnemonic, PATH);
+  const Zpub = msWallet.convertXpubToMultisignatureXpub(xpub);
+  const xfp = MultisigHDWallet.seedToFingerprint(mnemonic);
+  store.cosignerExport = JSON.stringify({xfp, xpub: Zpub, path: PATH});
+}
+
+export function initCosignerExport() {
+  _loadCosignerExport();
+  nav.goTo('CosignerExport');
+}
+
+export async function shareCosigner() {
+  try {
+    await _shareCosigner();
+  } catch (err) {
+    alert.error({err});
+  }
+}
+
+async function _shareCosigner() {
+  const xfp = JSON.parse(store.cosignerExport).xfp;
+  const filePath = `${RNFS.DocumentDirectoryPath}/mmxp-${xfp}.json`;
+  await RNFS.writeFile(filePath, store.cosignerExport, 'utf8');
+  await RNShare.open({
+    url: `file://${filePath}`,
+    type: 'application/json',
+  });
+  await RNFS.unlink(filePath);
+}
+
+//
+// Import ColdCard
+//
+
 export async function importColdCard() {
   try {
     await _importColdCardFile();
@@ -37,7 +82,7 @@ async function _createMultiSig() {
   if (multisig) {
     throw new Error('Multisig wallet already exists!');
   }
-  const mnemonic = await getWallet().getSecret();
+  const mnemonic = getWallet().getSecret();
   const msWallet = new MultisigHDWallet();
   msWallet.addCosigner(mnemonic);
   if (!store.cosigners.length) {
@@ -46,12 +91,16 @@ async function _createMultiSig() {
   store.cosigners.forEach(cosigner => {
     msWallet.addCosigner(cosigner.xpub, cosigner.fingerprint);
   });
-  msWallet.setDerivationPath("m/48'/0'/0'/2'");
+  msWallet.setDerivationPath(PATH);
   msWallet.setM(2);
   walletStore.wallets.push(msWallet);
   await walletStore.saveToDisk();
 }
 
+//
+// Export Multisig.txt
+//
+
 export async function exportTxtFile() {
   try {
     await _exportMultiSigTxt();

src/screen/cosigner-export.js

@@ -0,0 +1,52 @@
+import React from 'react';
+import {StyleSheet, View} from 'react-native';
+import {observer} from 'mobx-react';
+
+import {QRCode} from '../component/qrcode';
+import {PillButton} from '../component/button';
+import {LargeSpinner} from '../component/spinner';
+import {font} from '../component/style';
+
+import store from '../store';
+import * as wallet from '../action/wallet';
+import * as multisig from '../action/multisig';
+
+const styles = StyleSheet.create({
+  wrapper: {
+    flex: 1,
+    alignItems: 'center',
+    justifyContent: 'center',
+    padding: 25,
+  },
+  codeWrapper: {
+    flex: 1,
+    alignItems: 'center',
+    justifyContent: 'center',
+  },
+  addressText: {
+    marginTop: 20,
+    fontSize: font.sizeSub,
+    lineHeight: font.lineHeightSub,
+  },
+});
+
+const CosignerExportScreen = ({navigation}) => {
+  return (
+    <View style={styles.wrapper}>
+      {store.cosignerExport ? <Cosigner /> : <LargeSpinner />}
+    </View>
+  );
+};
+
+const Cosigner = () => (
+  <View>
+    <View style={styles.codeWrapper}>
+      <QRCode size={260}>{store.cosignerExport}</QRCode>
+    </View>
+    <PillButton onPress={() => multisig.shareCosigner()}>
+      Share Cosigner
+    </PillButton>
+  </View>
+);
+
+export default observer(CosignerExportScreen);

src/screen/settings.js

@@ -14,7 +14,7 @@ const styles = StyleSheet.create({
     padding: 15,
   },
   btnWrapper: {
-    marginTop: 50,
+    marginTop: 40,
     alignItems: 'center',
   },
 });
@@ -31,6 +31,12 @@ const SettingsScreen = () => (
     <View style={styles.btnWrapper}>
       <Button title="Change PIN" onPress={() => backup.initPinChange()} />
     </View>
+    <View style={styles.btnWrapper}>
+      <Button
+        title="Export Cosigner"
+        onPress={() => multisig.initCosignerExport()}
+      />
+    </View>
     <View style={styles.btnWrapper}>
       <Button
         title="Import ColdCard"

src/store.js

@@ -13,6 +13,7 @@ const store = observable({
   balanceRefreshing: false,
   transactions: [],
   nextAddress: null,
+  cosignerExport: null,
   cosigners: [],
 
   // screens