BIO_hex_string
BIO_hex_string(out, indent + 16, 16, sct->sct, sct->sct_len);
BIO_hex_string(out, indent + 16, 16, sct->log_id, sct->log_id_len);
BIO_hex_string(out, indent + 16, 16, sct->ext, sct->ext_len);
BIO_hex_string(out, indent + 16, 16, sct->sig, sct->sig_len);