Binding the Target Board to the ATECC608A Device

This binding process is meant to protect against an adversary who may cut the wire(s) between the ATECC608A device and the host MCU. It also helps to prevent the ATECC608A device from being removed from the board to use on another. This helps restrict the impact to only one board if the attacker manages to extract the IO protection secret from the MCU.

No user intervention is needed for this step. Once the target board detects a crypto-device and the IO protection secret is not set on either the host MCU or on the crypto-device, it initiates the process.

Once the binding is done with a crypto-device, the target board initiates the BOOTPROT fuse setting. This disables all further writes to the Bootloader section of the target board.

At the end of this process, both the SAMD21 and the crypto-device are bound and have their unique IO protection secret.

Note: Once the binding between the crypto-device and the host MCU is completed, it is not possible to rebind them after erasing the IO protection secret of the host MCU.