diff --git a/lib/types/backup-types.js b/lib/types/backup-types.js
--- a/lib/types/backup-types.js
+++ b/lib/types/backup-types.js
@@ -17,3 +17,19 @@
   backupDataKey: t.String,
   backupLogDataKey: t.String,
 });
+
+// This type should match `SIWEBackupData` in
+// `native/native_rust_library/src/backup.rs`
+export type SIWEBackupData = {
+  +backupID: string,
+  +siweBackupMsgNonce: string,
+  +siweBackupMsgStatement: string,
+  +siweBackupMsgIssuedAt: string,
+};
+export const siweBackupDataValidator: TInterface<SIWEBackupData> =
+  tShape<SIWEBackupData>({
+    backupID: t.String,
+    siweBackupMsgNonce: t.String,
+    siweBackupMsgStatement: t.String,
+    siweBackupMsgIssuedAt: t.String,
+  });
diff --git a/native/backup/use-client-backup.js b/native/backup/use-client-backup.js
--- a/native/backup/use-client-backup.js
+++ b/native/backup/use-client-backup.js
@@ -4,21 +4,18 @@
 
 import { isLoggedIn } from 'lib/selectors/user-selectors.js';
 import { accountHasPassword } from 'lib/shared/account-utils.js';
+import {
+  type SIWEBackupData,
+  siweBackupDataValidator,
+} from 'lib/types/backup-types.js';
 import type { SIWEBackupSecrets } from 'lib/types/siwe-types.js';
+import { assertWithValidator } from 'lib/utils/validation-utils.js';
 
 import { fetchNativeKeychainCredentials } from '../account/native-credentials.js';
 import { commCoreModule } from '../native-modules.js';
 import { persistConfig } from '../redux/persist.js';
 import { useSelector } from '../redux/redux-utils.js';
 
-type SIWEBackupData = {
-  +backupID: string,
-  +siweBackupMsg: string,
-  +siweBackupMsgNonce: string,
-  +siweBackupMsgStatement: string,
-  +siweBackupMsgIssuedAt: string,
-};
-
 type ClientBackup = {
   +uploadBackupProtocol: () => Promise<void>,
   +restorePasswordUserBackupProtocol: () => Promise<void>,
@@ -86,7 +83,6 @@
     );
 
     console.info('Backup restored.');
-    return;
   }, [currentUserID, loggedIn, currentUserInfo]);
 
   const retrieveLatestSIWEBackupData = React.useCallback(async () => {
@@ -102,8 +98,11 @@
 
     const serializedBackupData =
       await commCoreModule.retrieveLatestSIWEBackupData();
-    const siweBackupData: SIWEBackupData = JSON.parse(serializedBackupData);
-    return siweBackupData;
+
+    return assertWithValidator(
+      JSON.parse(serializedBackupData),
+      siweBackupDataValidator,
+    );
   }, [currentUserID, currentUserInfo, loggedIn]);
 
   return {
diff --git a/native/native_rust_library/src/backup.rs b/native/native_rust_library/src/backup.rs
--- a/native/native_rust_library/src/backup.rs
+++ b/native/native_rust_library/src/backup.rs
@@ -202,6 +202,34 @@
     });
   }
 
+  fn get_siwe_backup_data_from_msg(
+    backup_id: String,
+    siwe_backup_msg: String,
+  ) -> Result<SIWEBackupData, String> {
+    let siwe_backup_msg_obj: Message = match siwe_backup_msg.parse() {
+      Ok(siwe_backup_msg_obj) => siwe_backup_msg_obj,
+      Err(error) => {
+        return Err(error.to_string());
+      }
+    };
+
+    let siwe_backup_msg_nonce = siwe_backup_msg_obj.nonce;
+    let siwe_backup_msg_statement = match siwe_backup_msg_obj.statement {
+      Some(statement) => statement,
+      None => {
+        return Err("Backup message invalid: missing statement".to_string());
+      }
+    };
+
+    let siwe_backup_msg_issued_at = siwe_backup_msg_obj.issued_at.to_string();
+
+    Ok(SIWEBackupData {
+      backup_id,
+      siwe_backup_msg_nonce,
+      siwe_backup_msg_statement,
+      siwe_backup_msg_issued_at,
+    })
+  }
   pub fn retrieve_latest_siwe_backup_data(promise_id: u32) {
     RUNTIME.spawn(async move {
       let result = download_latest_backup_id()
@@ -222,32 +250,20 @@
         siwe_backup_msg,
       } = result;
 
-      let siwe_backup_msg_string = match siwe_backup_msg {
-        Some(siwe_backup_msg_value) => siwe_backup_msg_value,
-        None => {
-          string_callback(
-            "Backup message unavailable".to_string(),
-            promise_id,
-            "".to_string(),
-          );
-          return;
+      let siwe_backup_data = match siwe_backup_msg {
+        Some(siwe_backup_msg_value) => {
+          match get_siwe_backup_data_from_msg(backup_id, siwe_backup_msg_value)
+          {
+            Ok(data) => data,
+            Err(err) => {
+              string_callback(err, promise_id, "".to_string());
+              return;
+            }
+          }
         }
-      };
-
-      let siwe_backup_msg_obj: Message = match siwe_backup_msg_string.parse() {
-        Ok(siwe_backup_msg_obj) => siwe_backup_msg_obj,
-        Err(error) => {
-          string_callback(error.to_string(), promise_id, "".to_string());
-          return;
-        }
-      };
-
-      let siwe_backup_msg_nonce = siwe_backup_msg_obj.nonce;
-      let siwe_backup_msg_statement = match siwe_backup_msg_obj.statement {
-        Some(statement) => statement,
         None => {
           string_callback(
-            "Backup message invalid: missing statement".to_string(),
+            "Backup message unavailable".to_string(),
             promise_id,
             "".to_string(),
           );
@@ -255,16 +271,6 @@
         }
       };
 
-      let siwe_backup_msg_issued_at = siwe_backup_msg_obj.issued_at.to_string();
-
-      let siwe_backup_data = SIWEBackupData {
-        backup_id: backup_id,
-        siwe_backup_msg: siwe_backup_msg_string,
-        siwe_backup_msg_nonce: siwe_backup_msg_nonce,
-        siwe_backup_msg_statement: siwe_backup_msg_statement,
-        siwe_backup_msg_issued_at: siwe_backup_msg_issued_at,
-      };
-
       let serialize_result = serde_json::to_string(&siwe_backup_data);
       handle_string_result_as_callback(serialize_result, promise_id);
     });
@@ -456,12 +462,12 @@
   backup_log_data_key: String,
 }
 
+// This struct should match `SIWEBackupData` in `lib/types/backup-types.js`
 #[derive(Debug, Serialize)]
 #[serde(rename_all = "camelCase")]
 struct SIWEBackupData {
   #[serde(rename = "backupID")]
   backup_id: String,
-  siwe_backup_msg: String,
   siwe_backup_msg_statement: String,
   siwe_backup_msg_nonce: String,
   siwe_backup_msg_issued_at: String,