cap_channel_t *capcas, *caprandom;
unsigned char buf[16];
int i;

/* Open capability to Casper. */
capcas = cap_init();
if (capcas == NULL)
	err(1, "Unable to contact Casper");

/* Enter capability mode sandbox. */
if (cap_enter() < 0 && errno != ENOSYS)
	err(1, "Unable to enter capability mode");

/* Use Casper capability to create capability to the system.random service. */
caprandom = cap_service_open(capcas, "system.random");
if (caprandom == NULL)
	err(1, "Unable to open system.random service");

/* Close Casper capability, we don't need it anymore. */
cap_close(capcas);

/* Obtain entropy. */
if (cap_random_buf(caprandom, buf, sizeof(buf)) < 0)
	err(1, "Unable to obtain entropy");

for (i = 0; i < sizeof(buf); i++)
	printf("%.2x ", buf[i]);
printf("\n");