stop 'encrypted database' experiment

this PR removes options to create encrypted database.
existing encrypted databases will continue working for now.

the 'encrypted database' experiment started some years ago
was never finishes and already stopped working partly,
eg. importing backups as encrypted accounts stopped working
some years ago for newer android.

in the light of Signal's "encryption key flaw",
but also recent issues with worsending core things in Delta Chat,
it seems wise to concentrate on the core things ("you have one job!"),
and not on side topics comparable few persons are interested in.

also, it will become harder to maintain that path on upcoming api changes,
leaving the database open as opening is slow is needed but will become harder,
this will make notifications tricy,
may need additional effort to run in background etc.

all that is doable,
however, it will remove resources from far more important parts,
dangerously up to a level that breaks the app - a focus is limited.

also, no one really complained as it is already partly not-working,
it was _never_ working on desktop
(where it would make much more sense),
removal on iOS was flawless, see https://github.com/deltachat/deltachat-ios/pull/2011

tl;dr: better leave the protection up to the operating system
and concentrate on other things.

jni/dc_wrapper.c

@@ -282,12 +282,6 @@ JNIEXPORT jint Java_com_b44t_messenger_DcAccounts_addAccount(JNIEnv *env, jobjec
 }
 
 
-JNIEXPORT jint Java_com_b44t_messenger_DcAccounts_addClosedAccount(JNIEnv *env, jobject obj)
-{
-    return dc_accounts_add_closed_account(get_dc_accounts(env, obj));
-}
-
-
 JNIEXPORT jint Java_com_b44t_messenger_DcAccounts_migrateAccount(JNIEnv *env, jobject obj, jstring dbfile)
 {
     CHAR_REF(dbfile);

src/main/java/com/b44t/messenger/DcAccounts.java

@@ -27,7 +27,6 @@ public class DcAccounts {
     public native void            setPushDeviceToken   (String token);
 
     public native int             addAccount           ();
-    public native int             addClosedAccount     ();
     public native int             migrateAccount       (String dbfile);
     public native boolean         removeAccount        (int accountId);
     public native int[]           getAll               ();

src/main/java/org/thoughtcrime/securesms/RegistrationActivity.java

@@ -56,7 +56,6 @@ import com.b44t.messenger.util.concurrent.ListenableFuture;
 import com.b44t.messenger.util.concurrent.SettableFuture;
 import com.google.android.material.textfield.TextInputEditText;
 
-import org.thoughtcrime.securesms.connect.AccountManager;
 import org.thoughtcrime.securesms.connect.DcEventCenter;
 import org.thoughtcrime.securesms.connect.DcHelper;
 import org.thoughtcrime.securesms.permissions.Permissions;
@@ -87,8 +86,6 @@ public class RegistrationActivity extends BaseActionBarActivity implements DcEve
     private TextView providerLink;
     private @Nullable DcProvider provider;
 
-    private CheckBox encryptCheckbox;
-
     private Group advancedGroup;
     private ImageView advancedIcon;
     private ProgressDialog progressDialog;
@@ -116,8 +113,6 @@ public class RegistrationActivity extends BaseActionBarActivity implements DcEve
         providerLink = findViewById(R.id.provider_link);
         providerLink.setOnClickListener(l -> onProviderLink());
 
-        encryptCheckbox = findViewById(R.id.encrypt_checkbox);
-
         advancedGroup = findViewById(R.id.advanced_group);
         advancedIcon = findViewById(R.id.advanced_icon);
         TextView advancedTextView = findViewById(R.id.advanced_text);
@@ -248,10 +243,6 @@ public class RegistrationActivity extends BaseActionBarActivity implements DcEve
             certCheck.setSelection(certCheckFlags);
             expandAdvanced = expandAdvanced || certCheckFlags != 0;
 
-            encryptCheckbox.setHeight(0);
-            encryptCheckbox.setClickable(false);
-            encryptCheckbox.setFocusable(false);
-
             if (expandAdvanced) { onAdvancedSettings(); }
         } else if (getIntent() != null && getIntent().getBundleExtra(ACCOUNT_DATA) != null) {
           // Companion app might have sent account data
@@ -599,35 +590,6 @@ public class RegistrationActivity extends BaseActionBarActivity implements DcEve
             return;
         }
 
-        if (encryptCheckbox.isChecked()) {
-            AccountManager accountManager = AccountManager.getInstance();
-
-            if (progressDialog != null) {
-                progressDialog.dismiss();
-                progressDialog = null;
-            }
-
-            progressDialog = new ProgressDialog(this);
-            progressDialog.setMessage(getString(R.string.one_moment));
-            progressDialog.setCanceledOnTouchOutside(false);
-            progressDialog.setCancelable(false);
-            progressDialog.show();
-
-            // Prevent the user from disabling the checkbox again, switching to unencrypted account is currently not implemented
-            encryptCheckbox.setEnabled(false);
-            Util.runOnBackground(() -> {
-                DcHelper.getEventCenter(this).removeObservers(this);
-                accountManager.switchToEncrypted(this);
-                // Event center changed, register for events again
-                registerForEvents();
-                Util.runOnMain(this::continueLogin);
-            });
-        } else {
-            continueLogin();
-        }
-    }
-
-    private void continueLogin() {
         setupConfig();
 
         if (progressDialog != null) {

src/main/java/org/thoughtcrime/securesms/WelcomeActivity.java

@@ -181,27 +181,11 @@ public class WelcomeActivity extends BaseActionBarActivity implements DcEventCen
                     } else {
                         final String backupFile = dcContext.imexHasBackup(imexDir.getAbsolutePath());
                         if (backupFile != null) {
-
-
-                            View gl = View.inflate(this, R.layout.dialog_with_checkbox, null);
-                            CheckBox encryptCheckbox = gl.findViewById(R.id.dialog_checkbox);
-                            TextView msg = gl.findViewById(R.id.dialog_message);
-
-                            // If we'd use both `setMessage()` and `setView()` on the same AlertDialog, on small screens the
-                            // "OK" and "Cancel" buttons would not be show. So, put the message into our custom view:
-                            msg.setText(String.format(getResources().getString(R.string.import_backup_ask), backupFile) );
-                            encryptCheckbox.setText("Encrypt database (highly experimental, use at your own risk)");
-                            int[]      tintAttr   = new int[]{android.R.attr.textColorSecondary};
-                            TypedArray typedArray = obtainStyledAttributes(tintAttr);
-                            int        color      = typedArray.getColor(0, Color.GRAY);
-                            typedArray.recycle();
-                            encryptCheckbox.setTextColor(color);
-
                             new AlertDialog.Builder(this)
                                     .setTitle(R.string.import_backup_title)
-                                    .setView(gl)
+                                    .setMessage(String.format(getResources().getString(R.string.import_backup_ask), backupFile))
                                     .setNegativeButton(android.R.string.cancel, null)
-                                    .setPositiveButton(android.R.string.ok, (dialog, which) -> startImport(backupFile, null, encryptCheckbox.isChecked()))
+                                    .setPositiveButton(android.R.string.ok, (dialog, which) -> startImport(backupFile, null))
                                     .show();
                         }
                         else {
@@ -216,38 +200,10 @@ public class WelcomeActivity extends BaseActionBarActivity implements DcEventCen
                 .execute();
     }
 
-    private void startImport(@Nullable final String backupFile, final @Nullable Uri backupFileUri, boolean encrypt)
+    private void startImport(@Nullable final String backupFile, final @Nullable Uri backupFileUri)
     {
         notificationController = GenericForegroundService.startForegroundTask(this, getString(R.string.import_backup_title));
 
-        if (encrypt) {
-            AccountManager accountManager = AccountManager.getInstance();
-
-            if (progressDialog != null) {
-                progressDialog.dismiss();
-                progressDialog = null;
-            }
-
-            progressDialog = new ProgressDialog(this);
-            progressDialog.setMessage(getString(R.string.one_moment));
-            progressDialog.setCanceledOnTouchOutside(false);
-            progressDialog.setCancelable(false);
-            progressDialog.show();
-
-            Util.runOnBackground(() -> {
-                DcHelper.getEventCenter(this).removeObservers(this);
-                accountManager.switchToEncrypted(this);
-                // Event center changed, register for events again
-                registerForEvents();
-                Util.runOnMain(() -> continueStartBackup(backupFile, backupFileUri));
-            });
-        } else {
-            continueStartBackup(backupFile, backupFileUri);
-        }
-
-    }
-
-    private void continueStartBackup(String backupFile, Uri backupFileUri) {
         if( progressDialog!=null ) {
             progressDialog.dismiss();
             progressDialog = null;
@@ -411,7 +367,7 @@ public class WelcomeActivity extends BaseActionBarActivity implements DcEventCen
                 Log.e(TAG, " Can't import null URI");
                 return;
             }
-            startImport(null, uri, false);
+            startImport(null, uri);
         }
     }
 

src/main/java/org/thoughtcrime/securesms/connect/AccountManager.java

@@ -139,28 +139,6 @@ public class AccountManager {
         }
     }
 
-    /**
-     * Deletes the current account (must be unconfigured) and creates an encrypted account instead.
-     * @throws IllegalStateException if the currently selected account is already configured.
-     */
-    public void switchToEncrypted(Activity activity) {
-        Log.i(TAG, "Switching to encrypted account...");
-        DcAccounts accounts = DcHelper.getAccounts(activity);
-        DcContext selectedAccount = accounts.getSelectedAccount();
-        if (selectedAccount.isConfigured() == 1) {
-            throw new IllegalStateException("Can't switch to encrypted account if already configured");
-        }
-
-        int selectedAccountId = selectedAccount.getAccountId();
-        accounts.addClosedAccount();
-        accounts.removeAccount(selectedAccountId);
-
-        DcContext newAccount = accounts.getSelectedAccount();
-        DatabaseSecret secret = DatabaseSecretProvider.getOrCreateDatabaseSecret(activity, newAccount.getAccountId());
-        newAccount.open(secret.asString());
-        resetDcContext(activity);
-    }
-
     // ui
 
     public void showSwitchAccountMenu(Activity activity) {

src/main/res/layout/registration_activity.xml

@@ -122,7 +122,7 @@
             android:layout_height="wrap_content"
             android:visibility="gone"
             tools:visibility="visible"
-            app:constraint_referenced_ids="encrypt_checkbox, inbox, imap_login, imap_server, imap_port, imap_security_label, imap_security, outbox_view_spacer_top,
+            app:constraint_referenced_ids="inbox, imap_login, imap_server, imap_port, imap_security_label, imap_security, outbox_view_spacer_top,
             outbox, smtp_login, smtp_password, smtp_server, smtp_port, smtp_security_label, smtp_security, auth_method_label, auth_method, cert_check_label, cert_check, view_log_button, socks5_switch" />
 
         <ImageView
@@ -151,17 +151,6 @@
             app:layout_constraintStart_toEndOf="@id/advanced_icon"
             app:layout_constraintTop_toBottomOf="@id/no_servers_hint" />
 
-        <CheckBox
-            android:id="@+id/encrypt_checkbox"
-            android:layout_width="0dp"
-            android:layout_height="wrap_content"
-            android:text="Encrypt database (highly experimental, use at your own risk)"
-            android:layout_marginTop="12dp"
-            android:layout_marginBottom="12dp"
-            app:layout_constraintStart_toStartOf="@id/guideline_root_start"
-            app:layout_constraintEnd_toEndOf="@id/guideline_root_end"
-            app:layout_constraintTop_toBottomOf="@id/advanced_text" />
-
         <TextView
             android:id="@+id/inbox"
             android:layout_width="wrap_content"
@@ -170,7 +159,7 @@
             android:layout_marginTop="8dp"
             android:text="@string/login_inbox"
             app:layout_constraintStart_toStartOf="@id/guideline_root_start"
-            app:layout_constraintTop_toBottomOf="@id/encrypt_checkbox" />
+            app:layout_constraintTop_toBottomOf="@id/advanced_text" />
 
         <com.google.android.material.textfield.TextInputLayout
             android:id="@+id/imap_login"