Index: gnome-shell-45.3/data/gnome-shell-theme.gresource.xml
===================================================================
--- gnome-shell-45.3.orig/data/gnome-shell-theme.gresource.xml
+++ gnome-shell-45.3/data/gnome-shell-theme.gresource.xml
@@ -13,6 +13,7 @@
     <file>gnome-shell-light.css</file>
     <file>gnome-shell-high-contrast.css</file>
     <file>gnome-shell-start.svg</file>
+    <file>noise-texture.png</file>
     <file>pad-osd.css</file>
     <file>process-working-light.svg</file>
     <file>process-working-dark.svg</file>
Index: gnome-shell-45.3/js/ui/screenShield.js
===================================================================
--- gnome-shell-45.3.orig/js/ui/screenShield.js
+++ gnome-shell-45.3/js/ui/screenShield.js
@@ -11,6 +11,7 @@ import St from 'gi://St';
 
 import * as Signals from '../misc/signals.js';
 
+import * as Background from './background.js';
 import * as GnomeSession from '../misc/gnomeSession.js';
 import * as OVirt from '../gdm/oVirt.js';
 import * as LoginManager from '../misc/loginManager.js';
@@ -23,6 +24,8 @@ import * as SmartcardManager from '../mi
 
 import {adjustAnimationTime} from '../misc/animationUtils.js';
 
+const LOCKDIALOG_BACKGROUND_SCHEMA = 'org.gnome.desktop.background.lockdialog';
+
 const SCREENSAVER_SCHEMA = 'org.gnome.desktop.screensaver';
 const LOCK_ENABLED_KEY = 'lock-enabled';
 const LOCK_DELAY_KEY = 'lock-delay';
@@ -32,6 +35,9 @@ const DISABLE_LOCK_KEY = 'disable-lock-s
 
 const LOCKED_STATE_STR = 'screenShield.locked';
 
+const BLUR_BRIGHTNESS = 0.55;
+const BLUR_SIGMA = 60;
+
 // ScreenShield animation time
 // - STANDARD_FADE_TIME is used when the session goes idle
 // - MANUAL_FADE_TIME is used for lowering the shield when asked by the user,
@@ -74,6 +80,16 @@ export class ScreenShield extends Signal
             name: 'lockDialogGroup',
         });
 
+        // Add background for this._lockDialogGroup
+        this._bgLockDialogGroup = new Clutter.Actor();
+        this._lockDialogGroup.add_actor(this._bgLockDialogGroup);
+        this._lockDialogGroup.set_child_below_sibling(this._bgLockDialogGroup, null);
+        this._bgManagersLockDialogGroup = [];
+
+        this._updateBgLockDialogGroup();
+        this._monitorsChangedId =
+            Main.layoutManager.connect('monitors-changed', this._updateBgLockDialogGroup.bind(this));
+
         this.actor.add_actor(this._lockScreenGroup);
         this.actor.add_actor(this._lockDialogGroup);
 
@@ -142,6 +158,15 @@ export class ScreenShield extends Signal
         this._cursorTracker = Meta.CursorTracker.get_for_display(global.display);
 
         this._syncInhibitor();
+
+        this.connect('destroy', this._onDestroy.bind(this));
+    }
+
+    _onDestroy() {
+        if (this._monitorsChangedId) {
+            Main.layoutManager.disconnect(this._monitorsChangedId);
+            delete this._monitorsChangedId;
+        }
     }
 
     async _getLoginSession() {
@@ -518,6 +543,53 @@ export class ScreenShield extends Signal
         this.emit('wake-up-screen');
     }
 
+    _createBgLockDialogGroup(monitorIndex) {
+        let monitor = Main.layoutManager.monitors[monitorIndex];
+        let widget = new St.Widget({
+            style_class: 'bgLockDialogGroup-background',
+            x: monitor.x,
+            y: monitor.y,
+            width: monitor.width,
+            height: monitor.height,
+        });
+
+        let bgManager = new Background.BackgroundManager({
+            container: widget,
+            monitorIndex,
+            controlPosition: false,
+            settingsSchema: LOCKDIALOG_BACKGROUND_SCHEMA
+        });
+
+        this._bgManagersLockDialogGroup.push(bgManager);
+
+        this._bgLockDialogGroup.add_child(widget);
+
+        const themeContext = St.ThemeContext.get_for_stage(global.stage);
+
+        let effect = new Shell.BlurEffect({
+            brightness: BLUR_BRIGHTNESS,
+            sigma: BLUR_SIGMA * themeContext.scale_factor,
+        });
+
+        this._scaleChangedId = themeContext.connect('notify::scale-factor', () => {
+            effect.sigma = BLUR_SIGMA * themeContext.scale_factor;
+        });
+
+        widget.add_effect(effect);
+    }
+
+    _updateBgLockDialogGroup() {
+        for (let i = 0; i < this._bgManagersLockDialogGroup.length; i++)
+            this._bgManagersLockDialogGroup[i].destroy();
+
+        this._bgManagersLockDialogGroup = [];
+        this._bgLockDialogGroup.destroy_all_children();
+
+        for (let i = 0; i < Main.layoutManager.monitors.length; i++)
+            this._createBgLockDialogGroup(i);
+    }
+
+
     get locked() {
         return this._isLocked;
     }