Signal brings encrypted local backups to iOS and desktop

Signal has added on-device chat backups to its iOS and desktop apps, completing the first phase of its backups project. The rollout covers Android, iOS, Linux, macOS and Windows. Signal introduced the feature on Android nearly a year ago.

Users can choose Signal-hosted backups or local backups stored on their devices. Hosted backups include up to 45 days of media and 128 KB per message for free users, or 100 GB in paid plans. Local backups have no size restrictions. Both options are end-to-end encrypted and require a recovery key. Signal says hosted backups also use a supplemental key that rotates daily inside a Trusted Execution Environment.

The update brings local backups to iOS and desktop and moves Android backups to the same cross-platform format. When users link a new device, it can retrieve older attachments missing from the chat. Signal says media is stored separately from the archive, with duplicate files stored once. Paying users can also remove old media from local storage while keeping thumbnails, then retrieve full files from hosted backups.

Backups omit disappearing messages set to vanish within 24 hours. During restoration, expired disappearing messages in local backups are skipped. Keeping both backup types does not cause hosted backups to erase local ones.

The 8.30 iOS release also enables direct iPhone-to-iPhone transfer over a local, end-to-end encrypted Wi-Fi Aware link. Signal says the link improves speed and reliability. The company says engineers will now focus on improving systems outside backups.