6.10 Sign Command
    The Sign command generates a signature over the 32-byte
            SHA-256 digest of an externally-generated message. The digest of the message is passed
            into the device as part of the Sign command. The ECC private key in
            Slot 0 is used to generate the signature. Signing of internal messages is not an option
            with the device.
If so desired, a monotonic counter can be configured for limited key use with the
                Sign command. 
