ext/ipp/sources/ippcp/pcpgfpecset.c

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/* 
//     Intel(R) Integrated Performance Primitives. Cryptography Primitives.
//     EC over GF(p^m) definitinons
// 
//     Context:
//        ippsGFpECSet()
//
*/

#include "owndefs.h"
#include "owncp.h"
#include "pcpgfpecstuff.h"
#include "pcpeccp.h"

/*F*
// Name: ippsGFpECSet
//
// Purpose: Sets up the parameters of an elliptic curve over a finite field
//
// Returns:                   Reason:
//    ippStsNullPtrErr              NULL == pEC
//                                  NULL == pA
//                                  NULL == pB
//
//    ippStsContextMatchErr         invalid pEC->idCtx
//                                  invalid pA->idCtx
//                                  invalid pB->idCtx
//
//    ippStsOutOfRangeErr           GFPE_ROOM(pA)!=GFP_FELEN(pGFE)
//                                  GFPE_ROOM(pB)!=GFP_FELEN(pGFE)
//
//    ippStsNoErr                   no error
//
// Parameters:
//    pA        Pointer to the coefficient A of the equation defining the elliptic curve
//    pB        Pointer to the coefficient B of the equation defining the elliptic curve
//    pEC       Pointer to the context of the elliptic curve
//
*F*/

IPPFUN(IppStatus, ippsGFpECSet,(const IppsGFpElement* pA,
                                const IppsGFpElement* pB,
                                IppsGFpECState* pEC))
{
   IPP_BAD_PTR1_RET(pEC);
   pEC = (IppsGFpECState*)( IPP_ALIGNED_PTR(pEC, ECGFP_ALIGNMENT) );
   IPP_BADARG_RET( !ECP_TEST_ID(pEC), ippStsContextMatchErr );

   IPP_BAD_PTR2_RET(pA, pB);
   IPP_BADARG_RET( !GFPE_TEST_ID(pA), ippStsContextMatchErr );
   IPP_BADARG_RET( !GFPE_TEST_ID(pB), ippStsContextMatchErr );

   {
      gsModEngine* pGFE = GFP_PMA(ECP_GFP(pEC));
      int elemLen = GFP_FELEN(pGFE);

      IPP_BADARG_RET( GFPE_ROOM(pA)!=GFP_FELEN(pGFE), ippStsOutOfRangeErr);
      IPP_BADARG_RET( GFPE_ROOM(pB)!=GFP_FELEN(pGFE), ippStsOutOfRangeErr);

      /* copy A */
      cpGFpElementPadd(ECP_A(pEC), elemLen, 0);
      cpGFpElementCopy(ECP_A(pEC), GFPE_DATA(pA), elemLen);
      /* and set up A-specific (a==0 or a==-3) if is */
      if(GFP_IS_ZERO(ECP_A(pEC), elemLen))
         ECP_SPECIFIC(pEC) = ECP_EPID2;

      cpGFpElementSetChunk(ECP_B(pEC), elemLen, 3);
      GFP_METHOD(pGFE)->encode(ECP_B(pEC), ECP_B(pEC), pGFE);
      GFP_METHOD(pGFE)->add(ECP_B(pEC), ECP_A(pEC), ECP_B(pEC), pGFE);
      if(GFP_IS_ZERO(ECP_B(pEC), elemLen))
         ECP_SPECIFIC(pEC) = ECP_STD;

      /* copy B */
      cpGFpElementPadd(ECP_B(pEC), elemLen, 0);
      cpGFpElementCopy(ECP_B(pEC), GFPE_DATA(pB), elemLen);
      /* and set type of affine infinity representation:
      // (0,1) if B==0
      // (0,0) if B!=0 */
      ECP_INFINITY(pEC) = GFP_IS_ZERO(ECP_B(pEC), elemLen);

      return ippStsNoErr;
   }
}