Persist notification data. Note that it will break the key storage for the session database.

libraries/androidutils/build.gradle.kts

@@ -27,5 +27,6 @@ dependencies {
     implementation(libs.timber)
     implementation(libs.androidx.corektx)
     implementation(libs.androidx.activity.activity)
+    implementation(libs.androidx.security.crypto)
     implementation(projects.libraries.core)
 }

libraries/androidutils/src/main/kotlin/io/element/android/libraries/androidutils/file/EncryptedFileFactory.kt

@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2023 New Vector Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.element.android.libraries.androidutils.file
+
+import android.content.Context
+import androidx.security.crypto.EncryptedFile
+import androidx.security.crypto.MasterKeys
+import java.io.File
+
+class EncryptedFileFactory(
+    private val context: Context,
+) {
+    fun create(file: File): EncryptedFile {
+        // We need to use the same key for all the encrypted files.
+        val masterKeyAlias = MasterKeys.getOrCreate(MasterKeys.AES256_GCM_SPEC)
+        return EncryptedFile.Builder(
+            file,
+            context,
+            masterKeyAlias,
+            EncryptedFile.FileEncryptionScheme.AES256_GCM_HKDF_4KB
+        ).build()
+    }
+}