refactor(wallet): typed SigningCancelledException with i18n message

assets/languages/strings_de.arb

@@ -204,6 +204,7 @@
   "registerPhoneNumberInvalid": "Telefonnummer ist erforderlich",
   "registerPhoneNumberOnlyDigits": "Nur Zahlen sind erlaubt",
   "registerPhoneNumberTooShort": "Telefonnummer ist zu kurz",
+  "registrationFailed": "Registrierung fehlgeschlagen:\n${message}",
   "registrationRequired": "Registrierung erforderlich",
   "registrationRequiredDescription": "Um RealUnit Token kaufen zu können, müssen Sie sich einmalig registrieren.",
   "reset": "Zurücksetzen",
@@ -254,6 +255,7 @@
   "settingsWalletBackupSubtitle2": "Dies ist die einzige Möglichkeit, Ihre Wallet wiederherzustellen.",
   "showSeed": "Seed anzeigen",
   "signature": "Signatur",
+  "signingCancelled": "Signatur abgebrochen — bitte BitBox erneut bestätigen",
   "signMessage": "Signierte Nachricht",
   "signMessageGet": "Signierte Nachricht abrufen",
   "skip": "Überspringen",

assets/languages/strings_en.arb

@@ -204,6 +204,7 @@
   "registerPhoneNumberInvalid": "Phone number is required",
   "registerPhoneNumberOnlyDigits": "Only numbers are allowed",
   "registerPhoneNumberTooShort": "Phone number is too short",
+  "registrationFailed": "Registration failed:\n${message}",
   "registrationRequired": "Registration required",
   "registrationRequiredDescription": "To purchase RealUnit tokens, you must register once.",
   "reset": "Reset",
@@ -254,6 +255,7 @@
   "settingsWalletBackupSubtitle2": "This is the only way to recover your wallet.",
   "showSeed": "Show Seed",
   "signature": "Signature",
+  "signingCancelled": "Signature cancelled — please confirm on the BitBox again",
   "signMessage": "Sign Message",
   "signMessageGet": "Get Sign Message",
   "skip": "Skip",

lib/packages/service/dfx/dfx_auth_service.dart

@@ -3,6 +3,7 @@ import 'dart:convert';
 
 import 'package:realunit_wallet/packages/config/api_config.dart';
 import 'package:realunit_wallet/packages/service/app_store.dart';
+import 'package:realunit_wallet/packages/wallet/exceptions/signing_cancelled_exception.dart';
 import 'package:realunit_wallet/packages/wallet/wallet_account.dart';
 
 abstract class DFXAuthService {
@@ -48,7 +49,7 @@ abstract class DFXAuthService {
 
     final signature = await wallet.signMessage(message).timeout(_signMessageTimeout);
     if (signature.isEmpty || signature == '0x') {
-      throw Exception('Wallet returned an empty signature');
+      throw const SigningCancelledException();
     }
     await appStore.sessionCache.saveSignature(walletAddress, signature);
 

lib/packages/wallet/eip712_signer.dart

@@ -3,6 +3,7 @@ import 'dart:convert';
 import 'package:eth_sig_util_plus/eth_sig_util_plus.dart';
 import 'package:realunit_wallet/packages/hardware_wallet/bitbox_credentials.dart';
 import 'package:realunit_wallet/packages/service/dfx/models/payment/sell/dto/eip7702/eip7702_data_dto.dart';
+import 'package:realunit_wallet/packages/wallet/exceptions/signing_cancelled_exception.dart';
 import 'package:web3dart/crypto.dart';
 import 'package:web3dart/web3dart.dart';
 
@@ -126,7 +127,7 @@ class Eip712Signer {
     // guard the empty sig would be sent to the backend and the abort would
     // be misread as a successful sign.
     if (signature.isEmpty || signature == '0x') {
-      throw Exception('Signature was empty — wallet may have been cancelled or disconnected');
+      throw const SigningCancelledException();
     }
     return signature;
   }

lib/packages/wallet/exceptions/signing_cancelled_exception.dart

@@ -0,0 +1,6 @@
+class SigningCancelledException implements Exception {
+  const SigningCancelledException();
+
+  @override
+  String toString() => 'SigningCancelledException';
+}

lib/screens/kyc/steps/registration/cubits/registration_submit/kyc_registration_submit_cubit.dart

@@ -66,7 +66,7 @@ class KycRegistrationSubmitCubit extends Cubit<KycRegistrationSubmitState> {
       }
     } catch (e) {
       developer.log(e.toString());
-      emit(KycRegistrationSubmitFailure(e.toString()));
+      emit(KycRegistrationSubmitFailure(e.toString(), cause: e));
       return;
     }
   }
@@ -92,7 +92,7 @@ class KycRegistrationSubmitCubit extends Cubit<KycRegistrationSubmitState> {
       emit(const KycRegistrationSubmitSuccess(RegistrationStatus.completed));
     } catch (e) {
       developer.log(e.toString());
-      emit(KycRegistrationSubmitFailure(e.toString()));
+      emit(KycRegistrationSubmitFailure(e.toString(), cause: e));
     }
   }
 

lib/screens/kyc/steps/registration/cubits/registration_submit/kyc_registration_submit_state.dart

@@ -22,11 +22,12 @@ class KycRegistrationSubmitSuccess extends KycRegistrationSubmitState {
 
 class KycRegistrationSubmitFailure extends KycRegistrationSubmitState {
   final String message;
+  final Object? cause;
 
-  const KycRegistrationSubmitFailure(this.message);
+  const KycRegistrationSubmitFailure(this.message, {this.cause});
 
   @override
-  List<Object?> get props => [message];
+  List<Object?> get props => [message, cause];
 }
 
 class KycRegistrationSubmitBitboxRequired extends KycRegistrationSubmitState {

lib/screens/kyc/steps/registration/kyc_registration_page.dart

@@ -4,11 +4,13 @@ import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
 import 'package:go_router/go_router.dart';
+import 'package:realunit_wallet/generated/i18n.dart';
 import 'package:realunit_wallet/packages/service/dfx/dfx_kyc_service.dart';
 import 'package:realunit_wallet/packages/service/dfx/models/country/country.dart';
 import 'package:realunit_wallet/packages/service/dfx/models/registration/registration_status.dart';
 import 'package:realunit_wallet/packages/service/dfx/models/registration/registration_user_type.dart';
 import 'package:realunit_wallet/packages/service/dfx/real_unit_registration_service.dart';
+import 'package:realunit_wallet/packages/wallet/exceptions/signing_cancelled_exception.dart';
 import 'package:realunit_wallet/screens/hardware_connect_bitbox/connect_bitbox_page.dart';
 import 'package:realunit_wallet/screens/home/bloc/home_bloc.dart';
 import 'package:realunit_wallet/screens/kyc/cubits/kyc/kyc_cubit.dart';
@@ -109,9 +111,12 @@ class _KycRegistrationViewState extends State<KycRegistrationView> {
             }
           }
           if (state is KycRegistrationSubmitFailure) {
+            final message = state.cause is SigningCancelledException
+                ? S.of(context).signingCancelled
+                : S.of(context).registrationFailed(state.message);
             ScaffoldMessenger.of(context).showSnackBar(
               SnackBar(
-                content: Text('Registration failed:\n${state.message}'),
+                content: Text(message),
                 backgroundColor: RealUnitColors.status.red600,
               ),
             );

test/packages/wallet/eip712_signer_test.dart

@@ -1,10 +1,32 @@
 import 'package:flutter_test/flutter_test.dart';
+import 'package:mocktail/mocktail.dart';
+import 'package:realunit_wallet/packages/hardware_wallet/bitbox_credentials.dart';
 import 'package:realunit_wallet/packages/service/dfx/models/country/country.dart';
 import 'package:realunit_wallet/packages/service/dfx/models/registration/registration.dart';
 import 'package:realunit_wallet/packages/service/dfx/models/registration/registration_user_type.dart';
 import 'package:realunit_wallet/packages/wallet/eip712_signer.dart';
+import 'package:realunit_wallet/packages/wallet/exceptions/signing_cancelled_exception.dart';
 import 'package:web3dart/web3dart.dart';
 
+class _MockBitboxCredentials extends Mock implements BitboxCredentials {}
+
+Future<String> _signWith(BitboxCredentials credentials) => Eip712Signer.signRegistration(
+  credentials: credentials,
+  chainId: 1,
+  type: RegistrationUserType.human.jsonName,
+  email: 'cancel@dfx.swiss',
+  name: 'Cancel User',
+  phoneNumber: '+41790000000',
+  birthday: '1990-01-01',
+  nationality: 'CH',
+  addressStreet: 'Teststrasse 1',
+  addressPostalCode: '8000',
+  addressCity: 'Zurich',
+  addressCountry: 'CH',
+  swissTaxResidence: true,
+  registrationDate: '2026-05-12',
+);
+
 void main() {
   late String privateKeyHex;
   late RegistrationUserType type;
@@ -79,5 +101,19 @@ void main() {
         '0xa11cb57186b9c9f9a09fafa7a3aa256ab14ca030d7eba89f35026b64925d617b3e2cb15349ca561fae5e431deed3f1aa69c7d391cfba80aa6111e753fa782ea21c',
       );
     });
+
+    for (final emptySignature in const ['', '0x']) {
+      test('throws SigningCancelledException when BitBox returns "$emptySignature"', () async {
+        final credentials = _MockBitboxCredentials();
+        when(
+          () => credentials.address,
+        ).thenReturn(EthereumAddress.fromHex('0x0000000000000000000000000000000000000001'));
+        when(
+          () => credentials.signTypedDataV4(any(), any()),
+        ).thenAnswer((_) async => emptySignature);
+
+        expect(() => _signWith(credentials), throwsA(isA<SigningCancelledException>()));
+      });
+    }
   });
 }