Smart cards/hardware tokens try to not make themselves easy targets, and many such microcontrollers have attempts (of varying success) to defend against limited

Smart cards/hardware tokens try to not make themselves easy targets, and many such microcontrollers have attempts (of varying success) to defend against limited degrees of physical access and make attacks evident. But in any case, given sufficient time and resources, the attacker will always win. Bottom line: It depends largely on who stole it and for how long - however, if someone knew enough to target stealing your hardware token/smart card, you are under targeted attack and your key's probably toast: revoke it. I would also gently caution that the elliptic curve routines provided by NXP should not be used over special prime fields (elliptic curves that are fast in software, i.e. just about everything except Brainpool) as they abuse the large (RSA) multiplier whose side-channel blinding was not designed for non-random fields. (Unless they've rewritten it since I last saw it?)