Anyone understand how Smartlock works?

I realise there are 3 major components - ignition barrel, BEM and ECU.

Now, somewhere along the line some codes are transfered.

Is it the infra-red modules on the back of the ignition barrel that transfer codes to the BEM, and then the BEM sends a signal to the ECU to let it know that everything is alright?

Or, does the ignition barrell send a signal to the BEM and then the BEM sends codes to the ECU?