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  /*
  //  Purpose:
  //     Cryptography Primitive.
  //     HASH based Mask Generation Functions
  //
  //  Contents:
  //        ippsMGF1_rmf()
  //
  */
  
  #include "owndefs.h"
  #include "owncp.h"
  #include "pcphash_rmf.h"
  #include "pcptool.h"
  
  /*F*
  //    Name: ippsMGF1
  //
  // Purpose: Mask Generation Functios.
  //
  // Returns:                Reason:
  //    ippStsNullPtrErr           pMask == NULL
  //                               pMethod ==NULL
  //    ippStsLengthErr            seedLen <0
  //                               maskLen <0
  //    ippStsNoErr                no errors
  //
  // Parameters:
  //    pSeed       pointer to the input stream
  //    seedLen     input stream length (bytes)
  //    pMaske      pointer to the ouput mask
  //    maskLen     desired length of mask (bytes)
  //    pMethod     hash method
  //
  //
  // Note.
  //    MGF1 defined in the IEEE P1363 standard.
  //    MGF1 defined in the ANSI X9.63 standard and frequently called KDF (key Generation Function).
  //    The fifference between MGF1 and MGF2 is negligible - counter i runs from 0 (in MGF1) and from 1 (in MGF2)
  *F*/
  IPPFUN(IppStatus, ippsMGF1_rmf,(const Ipp8u* pSeed, int seedLen, Ipp8u* pMask, int maskLen, const IppsHashMethod* pMethod))
  {
     IPP_BAD_PTR2_RET(pMask, pMethod);
     IPP_BADARG_RET((seedLen<0)||(maskLen<0), ippStsLengthErr);
  
     {
        /* hash specific */
        int hashSize = pMethod->hashLen;
  
        int i, outLen;
  
        __ALIGN8 IppsHashState_rmf hashCtx;
        ippsHashInit_rmf(&hashCtx, pMethod);
  
        if(!pSeed)
           seedLen = 0;
  
        for(i=0,outLen=0; outLen<maskLen; i++) { /* counter i runs from 0 */
           Ipp8u cnt[4];
           cnt[0] = (Ipp8u)((i>>24) & 0xFF);
           cnt[1] = (Ipp8u)((i>>16) & 0xFF);
           cnt[2] = (Ipp8u)((i>>8)  & 0xFF);
           cnt[3] = (Ipp8u)(i & 0xFF);
  
           ippsHashUpdate_rmf(pSeed, seedLen, &hashCtx);
           ippsHashUpdate_rmf(cnt,   4,       &hashCtx);
  
           if((outLen + hashSize) <= maskLen) {
              ippsHashFinal_rmf(pMask+outLen, &hashCtx);
              outLen += hashSize;
           }
           else {
              Ipp8u md[MAX_HASH_SIZE];
              ippsHashFinal_rmf(md, &hashCtx);
              CopyBlock(md, pMask+outLen, maskLen-outLen);
              outLen = maskLen;
           }
        }
  
        return ippStsNoErr;
     }
  }
  