Function may_stop 

fn may_stop(read_here: bool, card_here: bool) -> bool

Whether “Stop using this security key” is offered, and done: for a key read here; for one another device read, only on a device that can read a security key, where reading it again takes it back. Not on a phone: it cannot read one yet, so a stop there could never be undone there, and would only stop it encrypting your own copies (N5).