improved performance and battery usage on older devices

lib/push/push_message_handler.dart

@@ -178,11 +178,15 @@ class PushMessageHandler {
       devicePrivateKey: privateKey,
       serverPublicKey: serverPublicKey,
     );
-    if (!decryptor.verify(subjectBase64, signatureBase64)) {
+    final result = await decryptor.verifyAndDecryptInBackground(
+      subjectBase64,
+      signatureBase64,
+    );
+    if (!result.verified) {
       log('Push: signature verification failed');
       return;
     }
-    final subject = decryptor.decrypt(subjectBase64);
+    final subject = result.subject;
     if (subject == null) {
       log('Push: could not decrypt subject');
       return;