Signal has released version 8.30, marking the conclusion of a platform-wide rollout for its encrypted backup functionality. The capability, which debuted on Android approximately one year earlier, enables users to generate encrypted copies of their conversations and retrieve them across devices in case of device loss. The system offers two distinct backup approaches: Signal-hosted backups with limits of 45 days of media and 128 KB per message for free accounts (expanding to 100 GB for paid subscribers), and local backups stored directly on devices without capacity constraints.
Both backup methods employ encryption and demand a recovery key for decryption. Hosted backups incorporate an additional layer of security through a supplemental key that refreshes daily within a Trusted Execution Environment, providing enhanced protection and forward secrecy. Signal notes that an on-device backup recovery key maintains the ability to decrypt all previous backup files it created, regardless of storage location. This key's importance has not gone unnoticed by malicious actors, who have already begun targeting it following Signal's initial feature announcement.
The latest update introduces on-device backup functionality to iOS and desktop platforms while standardizing Android backups to employ a unified cross-platform format. When users activate a new device from their primary device, the system now retrieves older attachments that may be missing from the conversation history. Signal has restructured media storage to exist separately from backup archives, with duplicate files retained only once to reduce redundant backup and synchronization operations.
Subscribers to paid plans gain access to a new feature allowing them to remove outdated media from local storage while preserving thumbnail versions, with full media automatically restored from hosted backups as needed. The backup system intentionally excludes messages configured to disappear within 24 hours from both backup methods, preventing their inclusion in archives. For users maintaining both hosted and on-device backups, the hosted version does not automatically delete the local version. During restoration, expired disappearing messages from local backups are omitted.
The iOS client update in version 8.30 introduces direct iPhone-to-iPhone transfer capability, utilizing a local end-to-end encrypted Wi-Fi Aware connection that Signal states enhances transfer speed and dependability. Signal indicates this release concludes the initial phase of its backup project, with development efforts now shifting toward enhancements to other system components.