from ctr_drbg.h:126
typedef struct mbedtls_ctr_drbg_context
{
unsigned char counter[16];
int reseed_counter;
int prediction_resistance;
size_t entropy_len;
int reseed_interval;
mbedtls_aes_context aes_ctx;
int (*f_entropy)(void *, unsigned char *, size_t);
void *p_entropy;
#if defined(MBEDTLS_THREADING_C)
mbedtls_threading_mutex_t mutex;
#endif
}
mbedtls_ctr_drbg_context;