.. _eccpverifysm2:

ECCPVerifySM2
=============


Verifies authenticity of a digital signature over a message digest using
the SM2 scheme.


Syntax
------


IppStatus ippsECCPVerifySM2(const IppsBigNumState\* pMsgDigest, const
IppsECCPPointState\* pRegPublic, const IppsBigNumState\* pSignR, const
IppsBigNumState\* pSignS, IppECResult\* pResult, IppsECCPState\* pECC);


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


``ippcp.h``


Parameters
----------


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   :header-rows: 0

   * - pMsgDigest   
     - Pointer to the message digest *msg*.
   * - pRegPublic   
     - Pointer to the message sender's regular private key ``regPubKey``.
   * - pSignR   
     - Pointer to the integer *r* of the digital signature.
   * - pSignS   
     - Pointer to the integer *s* of the digital signature.
   * - pResult   
     - Pointer to the digital signature verification result.
   * - pECC   
     - Pointer to the context of the elliptic cryptosystem.




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


The function verifies authenticity of the digital signature, represented
as integer big numbers *r* and *s*, over a message digest *msg*. The
digital signature over the message digest *msg* must be computed using
the SM2 scheme
[`SM2 <bibliography.html>`__] by to the
`ECCPSignSM2 <eccpsignsm2.html>`__
function.


The scheme requires the following cryptosystem key set up by the message
sender:


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

   * - \ *regPubKey*\    
     - Message sender's regular private key.




You can generate and set up the key in a call to the
`ECCPGenKeyPair <eccpgenkeypair.html>`__
function.


The result of the digital signature verification can take one of these
values:


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   :header-rows: 0

   * - ippECValid   
     - The digital signature is valid.
   * - ippECInvalidSignature   
     - The digital signature is not valid.




Before calling ECCPVerifySM2, set up the domain parameters of the
elliptic curve in the \*pECC context by calling one of the functions:
`ECCPSet <eccpset.html>`__
or
`ECCPSetStdSM2 <eccpsetstd.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.
   * - ippStsContextMatchErr   
     - Indicates an error condition if one of the specified contexts is not valid.
   * - ippStsMessageErr   
     - Indicates an error condition if the value of *msg* pointed by pMsgDigest falls outside the range of [1, *n*-1] where *n* is the order of the elliptic curve base point *G*.
   * - ippStsRangeErr   
     - Indicates an error condition if the value of pSignR or pSignS is less than 0.