Add IterationWarningView

Config/App.xcconfig

@@ -6,5 +6,6 @@ SWIFT_UPCOMING_FEATURE_MEMBER_IMPORT_VISIBILITY = YES
 INFOPLIST_KEY_BaseBundleID = $(BASE_BUNDLE_ID)
 INFOPLIST_KEY_TeamID = $(TEAM_ID)
 INFOPLIST_KEY_AppGroupID = $(APP_GROUP_ID)
+INFOPLIST_KEY_NSFaceIDUsageDescription = SecureStorage uses Face ID to unlock protected Keychain items.
 
 CODE_SIGN_ENTITLEMENTS = SecureStorageSample/SecureStorageSample.entitlements

README.md

@@ -42,7 +42,7 @@ SharedPackage/
         └── Models/
             └── UserProfile.swift
 SecureStorageSample/
-├── ContentView.swift        # Tabbed navigation
+├── ContentView.swift        # List-based navigation
 ├── Models/
 │   ├── Credential.swift
 │   └── SampleLocationData.swift
@@ -112,6 +112,7 @@ The app demonstrates various storage configurations:
 ### Encrypted Storage
 - AES-256-GCM or ChaCha20-Poly1305 encryption
 - PBKDF2 or HKDF key derivation
+- PBKDF2 iteration count must remain consistent or existing data will not decrypt
 - Complete file protection
 - External key material example via `KeyMaterialProviding`
 - Global encryption configuration (Keychain service/account) in app `init`

SecureStorageSample/StorageKeys/EncryptedFileSystem/SessionLogsKey.swift

@@ -17,6 +17,7 @@ extension StorageKeys {
         let syncPolicy: SyncPolicy = .never
 
         init(iterations: Int = 10_000) {
+            // NOTE: PBKDF2 iterations must remain stable for existing data; changing this breaks decryption.
             self.security = .encrypted(.aes256(keyDerivation: .pbkdf2(iterations: iterations)))
         }
     }

SecureStorageSample/Views/EncryptedStorageDemo.swift

@@ -37,6 +37,9 @@ struct EncryptedStorageDemo: View {
                     Stepper("PBKDF2 Iterations: \(iterations)", value: $iterations, in: 1000...100000, step: 1000)
                         .font(.caption)
                     
+                    IterationWarningView()
+                        .padding(.top, Design.Spacing.xSmall)
+
                     Text("Higher iterations = more secure but slower")
                         .font(.caption2)
                         .foregroundStyle(.secondary)
@@ -211,3 +214,11 @@ struct EncryptedStorageDemo: View {
         EncryptedStorageDemo()
     }
 }
+
+private struct IterationWarningView: View {
+    var body: some View {
+        Text("PBKDF2 iterations must match the value used during encryption. Changing this after saving will prevent decryption.")
+            .font(.caption2)
+            .foregroundStyle(Color.Status.warning)
+    }
+}