3.2.1 Symmetric Keys

The parent symmetric secret key is stored in Slot 3 of the data zone and is 32 bytes (256 bits) in length. This key is based on SHA-256 cryptography and provides 128 bits of key strength. For the host (SHA105) device, the parent symmetric key must always be programmed into the device. For the client device, either the parent or a diversified key may be programmed into Slot 3.