make encryption backwards compatible

verification/lib/verification_bloc.dart

@@ -125,7 +125,8 @@ class VerificationBloc extends Bloc<VerificationEvent, VerificationState> {
         }
         if (response.ticket != null && response.ticket!.isNotEmpty) {
           _ticket = response.ticket;
-          _writeEncryptedTicket(_ticket!);
+          //_writeEncryptedTicket(_ticket!);
+          await _ticketStore!.writeAsString(_ticket!, flush: true);
           yield VerificationState.unverified;
           add(VerificationEvent.check());
         }
@@ -179,7 +180,16 @@ class VerificationBloc extends Bloc<VerificationEvent, VerificationState> {
     if (ticket.isNotEmpty) {
       final iv = IV.fromBase64(ticket.substring(0, 24));
       final encrypted = Encrypted.fromBase64(ticket.substring(24));
-      _ticket = _encrypter!.decrypt(encrypted, iv: iv);
+      try {
+        _ticket = _encrypter!.decrypt(encrypted, iv: iv);
+      } catch (e) {
+        // convert old ticket into encrypted
+        _writeEncryptedTicket(ticket);
+        _log.info('restarting loadTicket with migrated ticket');
+        _loadTicket();
+        return;
+      }
+
       add(VerificationEvent.check());
     } else {
       _log.fine('ticket empty, going to noTicket state');
@@ -189,9 +199,9 @@ class VerificationBloc extends Bloc<VerificationEvent, VerificationState> {
 
   Future<void> _writeEncryptedTicket(String ticket) async {
     final iv = IV.fromLength(16);
-    print(iv.base64.length); // 24
+    // write 24 characters of IV and append encrypted data to ticketStore
     await _ticketStore!.writeAsString(
-      iv.base64 + _encrypter!.encrypt(_ticket!, iv: iv).base64,
+      iv.base64 + _encrypter!.encrypt(ticket, iv: iv).base64,
       flush: true,
     );
   }