apparently threema also uses google for notifications on android:
"Threema uses Firebase Cloud Messaging (FCM) to notify the app of new messages in the background. If Google Play Services are not installed, Threema checks for new messages using polling. The polling interval is configurable between 5 and 30 minutes and may cause additional battery drain and data usage."
but, apparently doesn't transmit any messages via fcm:
"Threema uses Firebase Cloud Messaging (FCM) to inform Android users about incoming messages in the background. The app then fetches messages directly from the Threema servers, decrypts them and displays a local notification. Neither contents nor details about messages are transmitted via FCM (the FCM payload is empty), and all of Firebase’s tracking and analysis components have been removed."
perhaps signal does something similar?
on ios, it apparently encrypts notification messages instead:
"Threema uses the Apple Push Notification Service (APNS) to inform recipients with iOS about new messages while the app is closed or in the background. The APNS message contains a payload that has been encrypted with a symmetric key, which is negotiated between the app and the Threema servers and is not known to Apple."
"Threema uses Firebase Cloud Messaging (FCM) to notify the app of new messages in the background. If Google Play Services are not installed, Threema checks for new messages using polling. The polling interval is configurable between 5 and 30 minutes and may cause additional battery drain and data usage."
but, apparently doesn't transmit any messages via fcm:
"Threema uses Firebase Cloud Messaging (FCM) to inform Android users about incoming messages in the background. The app then fetches messages directly from the Threema servers, decrypts them and displays a local notification. Neither contents nor details about messages are transmitted via FCM (the FCM payload is empty), and all of Firebase’s tracking and analysis components have been removed."
perhaps signal does something similar?
on ios, it apparently encrypts notification messages instead:
"Threema uses the Apple Push Notification Service (APNS) to inform recipients with iOS about new messages while the app is closed or in the background. The APNS message contains a payload that has been encrypted with a symmetric key, which is negotiated between the app and the Threema servers and is not known to Apple."