Not the Spark 1 or Spark 2, those are locked down and unbrickable.
Demo cards are for easier development, particularly for devs who don’t have or want implants but might be working to integrate some service. We will make them available on Dangerous Things for cheap. They will have some limitations coming down the pipe, but for now they are just like any other Spark 1 card (the cards have ISO15693 ICODE DNA chips like the Spark 1)
We program the keys during manufacture and keep the keys stored on our side. This is for authenticating the chip with challenge/response to the VivoKey platform.
It’s a random nonce actually, not a counter value… at least not the TAM1 challenge response. The SUN feature of the Spark 2 contains a CMAC signature that does use a counter value… but it’s technically less secure from an attack surface standpoint than TAM1, so we are only supporting it with a grain of salt at this point.