sc_get_challenge 3 opensc sc_get_challenge Request a challenge from a card #include <opensc.h> int sc_get_challenge(struct sc_card *card, unsigned char *rnd, size_t len); This function requests a challenge (i.e. random bytes) from card. The returned data will be stored in rnd, and will be len bytes long. Returns 0 if successful, or a negative value in case of error.