.. _ippsaes_gcmsetupnoise:

ippsAES_GCMSetupNoise
=====================

Turns on the mitigation for AES-GCM mode - the ``ippsAES_GCMDecrypt`` and ``ippsAES_GCMEncrypt`` processing functions.

Syntax
------

IppStatus ippsAES_GCMSetupNoise,(Ipp32u noiseLevel, IppsAES_GCMState* pState)

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

``ippcp.h``

Parameters
----------

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

   * - noiseLevel
     - The value of this parameter is directly proportional to the amount of noise to be injected.
       Increasing the noiseLevel by 1 means the delay (performance impact) is doubled.
   * - pState
     - Pointer to the ``IppsAES_GCMState`` context.

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

This function saves noise parameters in the pState context structure. A user-adjustable parameter is noiseLevel, it can be varied from 0 to 4. 
When processing function is called with this context it checks the context for the noiseLevel value and if it is non-zero, the function enables mitigation mechanism: 
the data passed to the processing function is divided into chunks, and each chunk is followed by probabilistic noise injection.  

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

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

   * - ippStsNullPtrErr
     - Indicates an error condition if pState pointer is NULL.
   * - ippStsContextMatchErr
     - Indicates an error condition if the pState parameter does not match the operation.
   * - ippStsLengthErr
     - Indicates an error if noiseLevel > 4.
   * - ippStsNotSupportedModeErr
     - Indicates an error condition if the AES-NI and VAES-NI instructions are not available on the target processor.
   * - ippStsNoErr 
     - Indicates no error. 
     

Any other value indicates an error or a warning.