.. _gfpecsetpointhash-gfpecsetpointhashbackcompatible-gfpecsetpointhash_rmf-gfpecsetpointhashbackcompatible_rmf:


GFpECSetPointHash, GFpECSetPointHashBackCompatible, GFpECSetPointHash_rmf, GFpECSetPointHashBackCompatible_rmf
==============================================================================================================


Constructs a point on an elliptic curve based on the hash of the input
message.


Syntax
------


IppStatus ippsGFpECSetPointHash(Ipp32u hdr, const Ipp8u\* pMsg, int
msgLen, IppsGFpECPoint\* pPoint, IppsGFpECState\* pEC, IppHashAlgId
hashID, Ipp8u\* pScratchBuffer);


IppStatus ippsGFpECSetPointHash_rmf(Ipp32u hdr, const Ipp8u\* pMsg, int
msgLen, IppsGFpECPoint\* pPoint, IppsGFpECState\* pEC, const
IppsHashMethod\* pMethod, Ipp8u\* pScratchBuffer);


IppStatus ippsGFpECSetPointHashBaskComatible(Ipp32u hdr, const Ipp8u\*
pMsg, int msgLen, IppsGFpECPoint\* pPoint, IppsGFpECState\* pEC,
IppHashAlgId hashID , Ipp8u\* pScratchBuffer);


IppStatus ippsGFpECSetPointHashBaskComatible_rmf(Ipp32u hdr, const
Ipp8u\* pMsg, int msgLen, IppsGFpECPoint\* pPoint, IppsGFpECState\* pEC,
const IppsHashMethod\* pMethod, Ipp8u\* pScratchBuffer);


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


``ippcp.h``


Parameters
----------


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

   * - hdr   
     - Header of the input message.
   * - pMsg   
     - Pointer to the input message.
   * - msgLen   
     - Length of the input message.
   * - pPoint   
     - Pointer to the IppsGFpECPoint context.
   * - pEC   
     - Pointer to the context of the elliptic curve.
   * - hashID   
     - ID of the hash algorithm used. For details, see `Supported Hash Algorithms <one-way-hash-primitives.html>`__.
   * - pMethod   
     - Predefined Hash Algorithm method. For details, see `Supported Hash Algorithms <one-way-hash-primitives.html>`__.
   * - pScratchBuffer   
     - Pointer to the scratch buffer. Can be NULL.




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


This function makes the coordinates of a point on the elliptic curve
over the finite field from a hash of the ``X``-coordinate. If the
pointer to the scratch buffer is NULL, the function uses a short
internal buffer for computations.


The ``X``-coordinate is computed by the following pseudocode formula:
``X = hash(hdr || message)``.


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


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

   * -     ippStsNoErr   
     -  Indicates no error. Any other value indicates an error or warning.
   * -     ippStsNullPtrErr   
     -  Indicates an error condition in the following cases:
        
        * ``pPoint`` or pEC is NULL.
        * Length of the message is more than zero, and the pointer pMsg is NULL.
        
   * -     ippStsContextMatchErr   
     -  Indicates an error condition if either pPoint or pEC context parameter does not match the operation.
   * -     ippStsBadArgErr   
     -  Indicates an error condition if the finite field over which the elliptic curve is initialized is not prime.
   * -     ippStsOutOfRangeErr   
     -  Indicates an error condition if the coordinates of the point pPoint do not belong to the finite field over which the elliptic curve is initialized.
   * -     ippStsLengthErr   
     -  Indicates an error condition if msgLen is negative.
   * -     ippStsQuadraticNonResidueErr   
     -  Indicates an error condition if the square of the ``Y``-coordinate of the point is a quadratic non-residue modulo ``p``.