How message encryption, backups and metadata fit together

Conversation mode changes the encryption boundary

Telegram distinguishes Cloud Chats, which use client-server/server-client encryption and cloud storage, from end-to-end encrypted Secret Chats. Secret Chats are tied to their originating devices. The same app therefore has different conversation modes; its name alone does not establish which one a conversation uses. Telegram: Cloud Chats and Secret Chats

A message backup can change who holds a recovery key

Apple's iCloud overview says that under standard protection, enabling iCloud Backup puts a copy of the Messages in iCloud encryption key in that backup. With Advanced Data Protection, the backup and that included key are end-to-end encrypted. Read the table's notes as well as its encryption label: Messages sync and device backup are related settings. Apple: cloud encryption, keys and metadata

Some cloud metadata have a separate protection scope

Apple says some metadata remain encrypted with Apple-held keys even with Advanced Data Protection. Its Messages examples include last-sync state, modification date, error codes and message type. Those fields are different from message text; their listing does not mean the encrypted conversation content is exposed. Apple: cloud encryption, keys and metadata

Optional backups have their own retention and recovery design

Signal describes Secure Backups as optional, end-to-end encrypted archives protected by a 64-character recovery key not shared with the service. Without that key, the service cannot decrypt or restore the archive. Disabling Secure Backups deletes the archive, so that switch is a data-loss decision as well as a privacy choice. Signal: secure backup help

Its 09-28-2026 update describes on-device backups across supported platforms, including iOS 8.30, and distinguishes their key behavior from hosted Secure Backups. An on-device recovery key can decrypt past saved backups wherever they remain. An old Android-only backup description does not cover the announced current design. Signal: 09-28-2026 backup update

Linked devices are additional places where chats can appear

Signal's linked-device help says chats and recent media can synchronize when a device is linked. Reviewing the primary device's linked-device list is therefore a different check from reviewing a backup archive. Secure transport does not mean that only one of your devices holds readable messages. Signal: linked-device review