.. _aesdecryptctr:


AESDecryptCTR
=============


Decrypts a variable length data stream in the CTR mode.


Syntax
------


IppStatus ippsAESDecryptCTR(const Ipp8u\* pSrc, Ipp8u\* pDst, int
srcLen,const IppsAESSpec\* pCtx, Ipp8u\* pCtrValue, int ctrNumBitSize);


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


``ippcp.h``


Parameters
----------


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

   * - pSrc   
     - Pointer to the input ciphertext data stream.
   * - pDst   
     - Pointer to the resulting plaintext data stream of a variable length.
   * - srcLen   
     - Length of the plaintext data stream in bytes.
   * - pCtx   
     - Pointer to the IppsAESSpec context.
   * - pCtrValue   
     - Pointer to the counter data block.
   * - ctrNumBitSize   
     - Number of bits in the specific part of the counter to be incremented.




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


The function decrypts the input data stream of a variable length
according to the CTR mode as specified in the [`NIST SP
800-38A <bibliography.html>`__].


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


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

   * - ippStsNoErr   
     - Indicates no error. Any other value indicates an error or warning.
   * - ippStsNullPtrErr   
     - Indicates an error condition if any of the specified pointers is NULL.
   * - ippStsLengthErr   
     - Indicates an error condition if the output data stream length is less than or equal to zero.
   * - ippStsCTRSizeErr    
     - Indicates an error condition if the value of the ctrNumBitSize is illegal.
   * - ippStsContextMatchErr   
     - Indicates an error condition if the context parameter does not match the operation.