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/* 
//     Intel(R) Integrated Performance Primitives. Cryptography Primitives.
//     Operations over GF(p).
// 
//     Context:
//        cpGFEqnr()
// 
// 
*/
#include "owndefs.h"
#include "owncp.h"

#include "pcpgfpstuff.h"
#include "pcpgfpxstuff.h"
#include "pcptool.h"

//tbcd: temporary excluded: #include <assert.h>

void cpGFEqnr(gsModEngine* pGFE)
{
   BNU_CHUNK_T* pQnr = GFP_QNR(pGFE);

   int elemLen = GFP_FELEN(pGFE);
   BNU_CHUNK_T* e = cpGFpGetPool(3, pGFE);
   BNU_CHUNK_T* t = e+elemLen;
   BNU_CHUNK_T* p1 = t+elemLen;
   //tbcd: temporary excluded: assert(NULL!=e);

   cpGFpElementCopyPadd(p1, elemLen, GFP_MNT_R(pGFE), elemLen);

   /* (modulus-1)/2 */
   cpLSR_BNU(e, GFP_MODULUS(pGFE), elemLen, 1);

   /* find a non-square g, where g^{(modulus-1)/2} = -1 */
   cpGFpElementCopy(pQnr, p1, elemLen);
   do {
      cpGFpAdd(pQnr, pQnr, p1, pGFE);
      cpGFpExp(t, pQnr, e, elemLen, pGFE);
      cpGFpNeg(t, t, pGFE);
   } while( !GFP_EQ(p1, t, elemLen) );

   cpGFpReleasePool(3, pGFE);
}