.. _gfpecpsigndsa-gfpecpsignnr-gfpecpsignsm2:

GFpECPSignDSA, GFpECPSignNR, GFpECPSignSM2
==========================================


Computes a digital signature over a message digest.


Syntax
------


IppStatus ippsGFpECSignDSA(const IppsBigNumState\* pMsgDigest, const
IppsBigNumState\* pRegPrivate, const IppsBigNumState\* pEphPrivate,
IppsBigNumState\* pSignR, IppsBigNumState\* pSignS, IppsGFpECState\*
pEC, Ipp8u\* pScratchBuffer);


IppStatus ippsGFpECSignNR(const IppsBigNumState\* pMsgDigest, const
IppsBigNumState\* pRegPrivate, const IppsBigNumState\* pEphPrivate,
IppsBigNumState\* pSignR, IppsBigNumState\* pSignS, IppsGFpECState\*
pEC, Ipp8u\* pScratchBuffer);


IppStatus ippsGFpECSignSM2(const IppsBigNumState\* pMsgDigest, const
IppsBigNumState\* pRegPrivate, const IppsBigNumState\* pEphPrivate,
IppsBigNumState\* pSignR, IppsBigNumState\* pSignS, IppsGFpECState\*
pEC, Ipp8u\* pScratchBuffer);


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


``ippcp.h``


Parameters
----------


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

   * - pMsgDigest   
     - Pointer to the message digest *msg* to be digitally signed, that is, to be ecrypted with a private key.
   * - pRegPrivate   
     - Pointer to the regular private key of the signer.
   * - pEphPrivate   
     - Pointer to the ephemeral private key of the signer.
   * - pSignR   
     - Pointer to the integer ``r`` of the digital signature.
   * - pSignS   
     - Pointer to the integer ``s`` of the digital signature.
   * - pEC   
     - Pointer to the context of the elliptic curve.
   * - pScratchBuffer   
     - Pointer to the scratch buffer.




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


Functions generate a digital signature respectively to DSA [`IEEE
P1362A <bibliography.html>`__],
Nyberg-Rueppel [`IEEE
P1362A <bibliography.html>`__] and SM2
[`SM2 <bibliography.html>`__] schemes.


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 any of the contexts pointed to by pMsgDigest, pRegPrivate, pEphPrivate, pSignR, pSignS, or pEC does not match the operation.
   * - ippStsMessageErr   
     - Indicates an error condition if the value of ``msg`` pointed to 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 any of the parameters pointed to by pSignR or pSignS has memory size that is smaller than the order ``n`` of the elliptic curve base point ``G``.
   * - ippStsIvalidPrivateKey   
     - Indicates an error condition if any of the parameters pointed to by pRegPrivate or pEphPrivate has memory size that is smaller than the order ``n`` of the elliptic curve base point ``G``.
   * - ippStsNotSupportedModeErr   
     - Indicates an error condition if the finite field GFp under the elliptic curve is not prime.
   * - ippStsEphemeralKeyErr   
     - Indicates an error condition if values of the ephemeral keys ``ephPrivKey`` and ``ephPubKey`` are not valid: the digital signature calculation returns ``r``\ =0 or ``s``\ =0 as a result.