.. _gfpecessetkey_sm2:

GFpECESSetKey_SM2
=================


Computes a shared secret.


Syntax
------


IppStatus ippsGFpECESSetKey_SM2(const IppsBigNumState\* pPrivate, const
IppsGFpECPoint\* pPublic, IppsECES_StateSM2\* pState, IppsGFpECState\*
pEC, Ipps8u\* pEcScratchBuffer);


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


``ippcp.h``


Parameters
----------


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

   * - pEC   
     - Pointer to the elliptic curve context used in the ECES.
   * - pState   
     - Pointer to the buffer being initialized as the ECES context.
   * - pPrivate   
     - Pointer to the own private keys of the elliptic curve.
   * - pPublic   
     - Pointer to the patry public key of the elliptic curve.
   * - pEcScratchBuffer   
     - Pointer to the scratch buffer for the elliptic curve.




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


The function computes a shared secret **Z** = [**Private**]\* **Public**
for future use.


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.
   * - ippStsContextMatchErr   
     - Indicates an error condition if the IppsGFpECState, IppsECES_StateSM2, IppsBigNumState, or IppsGFpECPoint context parameter does not match the operation.
   * - ippStsOutOfRangeErr   
     - Indicates an error conditions in the following cases:
       
       * Any of the specified pointers does not belong to the finite field over that the elliptic curve is initialized.
       * The scalar values does not belong to the finite field over that the elliptic curve is initialized.
       
   * - ippStsNotSupportedModeErr   
     - Indicates an error condition if the IppsGFpECState context parameter defines an elliptic curve over an extension of the prime finite field.
   * - ippStsBadArgErr   
     - Indicates an error condition if the IppsGFpECState context parameter has an element size that differs from the one used in the `ippsGFpECESInit_SM2 <gfpecesinit_sm2.html>`__ function call.
   * - ippStsPointAtInfinity   
     - Indicates an error condition if the IppsGFpECPoint context parameter defines a point at infinity.