.. _mbx_sm4_gcm_update_aad_mb16:

mbx_sm4_gcm_update_aad_mb16
===========================

Processes additional authenticated data (AAD).

Syntax
------

mbx_status16 mbx_sm4_gcm_update_aad_mb16(const int8u* pa_aad[SM4_LINES], const int aad_len[SM4_LINES], SM4_GCM_CTX_mb16* p_context); 


Include Files
-------------

``crypto_mb/sm4_gcm.h``

Parameters
----------

.. list-table:: 
   :header-rows: 0

   * - pa_aad
     - Array of pointers to the additional authenticated data.
   * - aad_len
     - Array of lengths of the additional authenticated data in bytes.
   * - p_context 
     - Pointer to the context to keep intermediate results between calls.


Description
-----------

Processes the additional authenticated data streams passed by ``pa_aad`` of a variable length passed through the ``aad_len`` array 
according to the GCM cipher scheme and updates context with the intermediate hash value.

.. note:: mbx_sm4_gcm_update_aad_mb16 has several call sequence restrictions. See :ref:`sm4_gsm_algorithm_functions` page for details.


Return Values
-------------

The ``mbx_sm4_gcm_update_aad_mb16()`` function returns the status that indicates whether the operation is completed successfully or not. 
The status value of 0 indicates that the key schedule is successfully initialized. 
In case of a non-zero status value, ``MBX_GET_HIGH_PART_STS16()`` and ``MBX_GET_LOW_PART_STS16()`` can help to get the low and high parts of ``mbx_status16``, 
which can be analyzed separately with the ``MBX_GET_STS()`` call. 
The low part includes the first eight statuses, while the high part includes the remaining eight statuses for each operation.