Understanding update-signed.zip : The Backbone of Android System Updates
) to distinguish the finalized, verified archive from the original, unsigned update.zip Verification Process
Below is a detailed, academic-style paper that treats update-signed.zip as a case study in secure software updates, covering its purpose, structure, security properties, and real-world implementation contexts. update-signed.zip
| Path within ZIP | Purpose |
|----------------|---------|
| payload.bin or system.img | Main system image (differential or full) |
| META-INF/com/android/otacert | Public key certificate(s) |
| META-INF/com/android/metadata | Metadata: version, device codename, timestamp, build fingerprint |
| META-INF/CERT.RSA | PKCS#7 signature of the entire archive (except signature block) |
| META-INF/CERT.SF | Signed manifest of individual file hashes |
| META-INF/MANIFEST.MF | List of SHA-256 digests of each file in the ZIP |
Rename for Simplicity: It is often easier to rename your file to update.zip or signed-ota_update.zip to avoid typing long characters in a terminal. Understanding update-signed
: Flashing an update signed for one device model onto another can cause a "hard brick," rendering the device unusable.
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 To generate a release image, use: make dist
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)