from nx_secure_x509.h:776
union
{
NX_SECURE_RSA_PRIVATE_KEY rsa_private_key;
#ifdef NX_SECURE_ENABLE_ECC_CIPHERSUITE
NX_SECURE_EC_PRIVATE_KEY ec_private_key;
#endif
struct
{
const UCHAR *key_data;
ULONG key_length;
} user_key;
} nx_secure_x509_private_key;