Signal Completes Cross-Platform Encrypted Backup Rollout
Signal has released version 8.30 of its messaging app, extending its secure local backup functionality to iOS and desktop platforms and finalizing the rollout of the feature across all supported operating systems, including Android, iOS, Linux, macOS, and Windows. The update ensures that users on any major platform can now create and restore end-to-end encrypted backups of their chat history without relying solely on cloud-based solutions.
The local backup option, which was first introduced on Android approximately one year prior, allows users to store encrypted backups directly on their devices with no imposed size restrictions. Unlike Signal-hosted backups, which enforce limits of 45 days of media and 128 KB per message for free-tier users (with 100 GB available in paid plans), local backups place no ceiling on data volume, making them suitable for users with extensive message histories or large media attachments.
How Signal’s Backup Encryption and Recovery Works
Both backup methods — hosted and on-device — rely on end-to-end encryption and require a recovery key to decrypt stored data. However, Signal-hosted backups incorporate an additional layer of security: a supplemental key that rotates daily within a Trusted Execution Environment (TEE), enhancing protection against compromise and supporting forward secrecy. In contrast, the recovery key for on-device backups remains static and can decrypt any backup file it created, regardless of where that file is stored or how it was transferred.
Signal emphasizes that possession of the on-device recovery key grants access to all previously encrypted backups, a characteristic that has drawn attention from threat actors. According to the company, malicious actors began incorporating this key into their targeting strategies shortly after the feature’s initial launch on Android, recognizing its value in accessing sensitive chat data.
Improvements in Backup Efficiency and Media Handling
Version 8.30 also introduces several optimizations to the backup system. Media files are now stored separately from the main backup archive, and duplicate files are retained only once, reducing storage overhead and eliminating redundant synchronization. This deduplication mechanism improves both backup speed and restore efficiency, particularly for users who frequently share images, videos, or documents.
For subscribers to Signal’s paid tier, a new feature enables automatic purging of full-resolution media from local device storage, retaining only thumbnails locally. When needed, the original files can be retrieved on demand from the user’s hosted backup, balancing local storage conservation with accessibility.
The backup system continues to respect user-defined privacy settings: messages configured to disappear within 24 hours are excluded from both hosted and on-device backups. If a user maintains both backup types, restoring from a local backup will skip any disappearing messages that have already expired, while the hosted backup remains unaffected and is not deleted during the restoration process.
Enhanced Device Transfer and Future Development Focus
In addition to backup improvements, the iOS-specific release of version 8.30 enables direct iPhone-to-iPhone transfer over a local, end-to-end encrypted connection using Wi-Fi Aware technology. Signal states that this method improves the speed and reliability of migrating chat data between Apple devices without relying on intermediate servers.
The company characterizes the release of version 8.30 as the completion of the first phase of its backups project. Moving forward, Signal’s engineering team will shift focus toward strengthening non-backup-related systems, including message encryption, protocol resilience, and overall app security against emerging threats.
Source: BleepingComputer