How to protect CSR bluecore firmware?

Hello!

Please, tell me, how protect csr bc04 firmware from clonning and changing?

Will signing of firmware helps? I have not found information about this in bluelab docs… where can i get some info about it?

May be is some invariant fields in chip that can be checked in individual compiled firmware? I have tryied to find one, but no luck. BT mac address, as example, but it also clonnable…

Any help?