Update-signed.zip (2024)

update-signed.zip file is a digitally signed package commonly used in Android for Over-the-Air (OTA) updates

or system modifications. Signing ensures the device's recovery system can verify the update's authenticity before installation. Android Open Source Project Core Components A standard update-signed.zip includes several key files within its structure: META-INF/com/google/android/update-binary : The executable that performs the update. META-INF/com/google/android/updater-script

: An Edify script containing the instructions for the update. META-INF/CERT.SF & CERT.RSA

: Digital signature files that verify the contents of the archive. System Files update-signed.zip

: The actual files (e.g., system images, apps, or binaries) being updated on the device. Google Groups How to Generate a Signed Update

You can create a signed ZIP using various tools depending on your environment: AOSP Tools ota_from_target_files script provided in the Android Open Source Project (AOSP)

repository to convert target files into a signed OTA package. update-signed

: A standalone Java tool used to sign the archive with a certificate and private key.

java -jar signapk.jar certificate.pem key.pk8 input.zip update-signed.zip

: A popular utility (often used with Magisk) for signing ZIP files directly on a device or via command line. Android Open Source Project Common Issues Sign builds for release - Android Open Source Project Cause: The update was incompatible, or you didn’t

To generate a release image, use: make dist sign_target_files_apks \ -o \ # explained in the next section --default_key_mappings ~ Android Open Source Project signing update.zip for stock recovery - Google Groups

3. Common Use Cases

II. Core Features & Capabilities

Error 4: Device won't boot after flashing (bootloop)

• Cause: The update was incompatible, or you didn’t wipe necessary partitions (especially when switching between Android versions or ROM families).
• Fixes:
  • Boot back into recovery.
  • Perform a factory reset / wipe data.
  • If that fails, restore a backup or flash the stock firmware.

8. Limitations and Future Directions

• Single key vulnerability – Many implementations use one key; loss or theft breaks security.
• No forward secrecy – Once device trusts a key, all past updates are compromised if key leaks.
• Large updates – update-signed.zip can exceed 2 GB; verification requires double I/O (hash then apply).
• Proposed improvements –
  • Merkle tree signatures (as in dm‑verity) to allow streaming authenticated installation.
  • Threshold signatures (e.g., 2‑of‑3 keys).
  • Use of cosign (Sigstore) or TUF to decouple signature storage from the ZIP.

9. Conclusion

The humble update-signed.zip encapsulates decades of systems security wisdom: separation of content from metadata, offline signing, online verification, and atomic update application. While not perfect, it provides a practical, deployable mechanism for secure updates on billions of devices. Understanding its design clarifies why filenames like update-signed.zip are more than mere conventions—they represent a compact security contract between the update author and the target system.