.. _mbx_sm4_gcm_init_context_mb16:

mbx_sm4_gcm_init_context_mb16
=============================

Initializes context by setting up all the necessary key material for both encryption and decryption operations, initializes the hash keys, and processes initialization vector (IV).

Syntax
------

mbx_status16 mbx_sm4_gcm_init_context_mb16(const sm4_key* pa_key[SM4_LINES], const int8u* pa_iv[SM4_LINES], const int iv_len[SM4_LINES],                  SM4_GCM_CTX_mb16* p_context);


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

``crypto_mb/sm4_gcm.h``

Parameters
----------

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

   * - pa_key
     - Array of pointers to the SM4 secret keys.
   * - pa_iv
     - Array of pointers to the initialization vectors.
   * - iv_len  
     - Array of lengths of the initialization vectors in bytes.
   * - p_context
     - Pointer to the context to keep intermediate results between calls.

Description
-----------
Sets up a key schedule using user-supplied secret keys passed through ``pa_key`` with all necessary key material for both encryption and decryption operations. 
Processes the initialization vector streams passed by ``pa_iv`` of a variable length passed through ``iv_len array`` according to the GCM cipher scheme and updates context with processing result.

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

The ``mbx_sm4_gcm_init_context_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 
the ``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.