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Security-And-Privacy.md

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Security and Privacy

Recommended device

The strongest configuration is a Pixel 8 or later running GrapheneOS.

Why:

  • Titan M2 secure element. Zigner stores seed encryption keys in StrongBox (the Titan M2). Key material never exists in main memory in plaintext. Even with physical access and a JTAG probe, an attacker cannot extract keys from the secure element without defeating its tamper mesh.

  • Verified boot with a locked bootloader. GrapheneOS uses its own signing keys. Zigner's device attestation treats both OEM-signed and self-signed verified boot as secure (bootloader locked either way). An unlocked bootloader is flagged as insecure because it allows booting a modified OS that could extract keys.

  • No known remote exploit chain. Leaked NSO Group capability documents from 2023 showed Pegasus had no working exploit chain against GrapheneOS on Pixel 6+ hardware. The Titan M2 (Pixel 8+) adds a stronger secure element on top of that.

  • Hardened memory allocator, per-profile encryption, reduced attack surface. GrapheneOS strips Google Play Services, tightens SELinux policy, and applies memory safety hardening that stock Android does not.

If you cannot get a Pixel, any device with StrongBox or a TEE (Trusted Execution Environment) provides hardware-backed key storage. Zigner detects what's available and reports it in Settings. Software-only key storage is explicitly flagged as insecure.

Device setup

  1. Factory reset the device.
  2. Install GrapheneOS (or your OS of choice).
  3. Enable full-disk encryption with a strong passphrase. Do not rely solely on biometrics for device unlock — fingerprints and face scans can be compelled.
  4. Install Zigner from GitHub Releases. Verify the APK checksum and signature.
  5. Enable airplane mode. Disable WiFi, Bluetooth, NFC, and cellular. Physically removing wireless hardware is better if the device allows it.
  6. Never connect the device to a computer. Only charge on a dedicated power adapter from the manufacturer.

What Zigner binds to hardware

On Android with StrongBox (Pixel 8+ Titan M2, Samsung Knox, etc.):

  • Seed encryption key is AES-256-GCM generated inside the secure element via setIsStrongBoxBacked(true). The key never leaves the element.
  • Key is invalidated if biometric enrollment changes (new fingerprint added).
  • Key requires the device to be unlocked and the user to authenticate within 30 seconds.
  • Device attestation checks the bootloader state, OS version, and security patch level before signing.

On iOS:

  • Seeds are stored in the Keychain with kSecAttrAccessibleWhenPasscodeSetThisDeviceOnly, backed by the Secure Enclave. The Keychain item is bound to the device and requires the device passcode.

Updating Zigner

Your device should never go online. To update:

  1. Verify you have the recovery phrase for every key set.
  2. Factory reset the device.
  3. Reinstall OS and Zigner, verify APK checksum.
  4. Re-enable airplane mode and disable all radios.
  5. Recover your accounts from seed phrases.

Data collection

None. Zigner makes zero network requests and collects no telemetry.