Our blog article specific to this topic can be found here: Whisper: How the secure Bluetooth integration of the BitBox02 Nova works

Main concept:

• Whisper is the custom secure Bluetooth integration for the BitBox02 Nova.

Why it matters:

• It enables the BitBox02 Nova to work with iPhone and iPad.
• It is designed to preserve user privacy and security.
• The design does not trust the Bluetooth stack.

Best practices:

• A dedicated Bluetooth chip is physically isolated from the main chip.
• The Bluetooth chip cannot access wallet secrets or flash storage.
• The main chip cryptographically verifies the Bluetooth firmware on every boot.
• The Bluetooth firmware is open-source for transparency.
• It enforces the highest Bluetooth security standard: LE Secure Connections.
• Pairing requires the user to confirm matching codes on both devices.
• Data has two layers of encryption: native Bluetooth and BitBox end-to-end.
• Bluetooth signal strength is minimized during the initial connection phase.
• Once connected, the signal strength is increased slightly for reliability.
• Before setup, the device uses a random Bluetooth name each time it powers on.
• After setup, the user can set a custom device name for Bluetooth.
• It uses random private addresses (RPA) to prevent passive tracking.
• The device prioritizes USB connection over Bluetooth.
• Bluetooth is turned off as soon as a USB connection is active.
• Users can permanently deactivate Bluetooth via a firmware setting.

Warnings:

• If you deactivate Bluetooth, you need a USB-enabled host device to re-activate it.
• Bluetooth cannot be re-activated using an iPhone or iPad.

Product details:

• The feature is available on the BitBox02 Nova.
• It uses Bluetooth Low Energy (BLE).
• The hardware includes a dedicated DA14531 MCU for Bluetooth.