Re-instate the mandatory verification banner (reverts #8015).

Riot/Modules/Application/LegacyAppDelegate.m

@@ -3376,8 +3376,7 @@ - (void)checkCrossSigningForSession:(MXSession*)mxSession
                 case MXCrossSigningStateCrossSigningExists:
                     MXLogDebug(@"[AppDelegate] handleAppState: presentVerifyCurrentSessionAlertIfNeededWithSession");
                     [self.masterTabBarController presentVerifyCurrentSessionAlertIfNeededWithSession:mxSession];
-                    // Temporarily disabled until we have a way to reset from the verification screen.
-                    // [self.masterTabBarController presentVerificationRequiredBannerWithSession:mxSession];
+                    [self.masterTabBarController presentVerificationRequiredBannerWithSession:mxSession];
                     break;
                 case MXCrossSigningStateCanCrossSign:
                     MXLogDebug(@"[AppDelegate] handleAppState: presentReviewUnverifiedSessionsAlertIfNeededWithSession");

Riot/Modules/Home/AllChats/AllChatsViewController.swift

@@ -849,7 +849,7 @@ extension AllChatsViewController: SplitViewMasterViewControllerProtocol {
     }
 
     func presentVerificationRequiredBanner(with session: MXSession) {
-        guard bannerView == nil else {
+        guard bannerView == nil, VerificationRequiredBannerChecker().canShowBanner(for: session) else {
             return
         }
 

Riot/Modules/Home/VerificationRequiredBanner/VerificationRequiredBannerChecker.swift

@@ -0,0 +1,22 @@
+// 
+// Copyright 2022-2024 New Vector Ltd.
+//
+// SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+// Please see LICENSE files in the repository root for full details.
+//
+
+import Foundation
+import CryptoKit
+
+struct VerificationRequiredBannerChecker {
+    func canShowBanner(for session: MXSession) -> Bool {
+        guard let userID = session.myUserId,
+              let serverName = MXTools.serverName(inMatrixIdentifier: userID),
+              let data = serverName.components(separatedBy: ".").suffix(2).joined(separator: ".").data(using: .utf8) else {
+            return true
+        }
+
+        let hash = SHA256.hash(data: data).map { String(format: "%02x", $0) }.joined()
+        return hash != "9e6d1ca3e739dd3f879b8046af783402a34d247f879dfa1b531edbd56a56c1a6"
+    }
+}

RiotTests/VerificationRequiredBannerCheckerTests.swift

@@ -0,0 +1,25 @@
+// 
+// Copyright 2026 Element Creations Ltd.
+//
+// SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+// Please see LICENSE files in the repository root for full details.
+//
+
+import XCTest
+
+@testable import Element
+
+class VerificationRequiredBannerCheckerTests: XCTestCase {
+    private let checker = VerificationRequiredBannerChecker()
+
+    func testCanShowBanner() {
+        XCTAssertTrue(checker.canShowBanner(for: makeSession(userID: "@user:example.com")))
+        XCTAssertTrue(checker.canShowBanner(for: makeSession(userID: "@user:matrix.org")))
+    }
+
+    private func makeSession(userID: String) -> MXSession! {
+        MXSession(matrixRestClient: .init(credentials: .init(homeServer: "",
+                                                             userId: userID,
+                                                             accessToken: "")))
+    }
+}