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  /* 
  // 
  //  Purpose:
  //     Cryptography Primitive.
  //     SMS4 encryption/decryption
  // 
  //  Contents:
  //        cpDecryptSMS4_cbc()
  //
  */
  
  #include "owncp.h"
  #include "pcpsms4.h"
  #include "pcptool.h"
  
  #if !defined _PCP_SMS4_DECRYPT_CBC_H
  #define _PCP_SMS4_DECRYPT_CBC_H
  
  /*F*
  //    Name: ippsSMS4DecryptCBC
  //
  // Purpose: SMS4-CBC decryption.
  //
  // Returns:                Reason:
  //    ippStsNullPtrErr        pCtx == NULL
  //                            pSrc == NULL
  //                            pDst == NULL
  //                            pIV  == NULL
  //    ippStsContextMatchErr   !VALID_SMS4_ID()
  //    ippStsLengthErr         len <1
  //    ippStsUnderRunErr       0!=(dataLen%MBS_SMS4)
  //    ippStsNoErr             no errors
  //
  // Parameters:
  //    pSrc        pointer to the source data buffer
  //    pDst        pointer to the target data buffer
  //    dataLen     input/output buffer length (in bytes)
  //    pCtx        pointer to the SMS4 context
  //    pIV         pointer to the initialization vector
  //
  *F*/
  static void cpDecryptSMS4_cbc(const Ipp8u* pIV,
                                const Ipp8u* pSrc, Ipp8u* pDst, int dataLen,
                                const IppsSMS4Spec* pCtx)
  {
     const Ipp32u* pRoundKeys = SMS4_DRK(pCtx);
  
     /* copy IV */
     Ipp32u iv[MBS_SMS4/sizeof(Ipp32u)];
     CopyBlock16(pIV, iv);
  
     /* do decryption */
     #if (_IPP>=_IPP_P8) || (_IPP32E>=_IPP32E_Y8)
     if(IsFeatureEnabled(ippCPUID_AES)) {
        int processedLen = cpSMS4_CBC_dec_aesni(pDst, pSrc, dataLen, pRoundKeys, (Ipp8u*)iv);
        pSrc += processedLen;
        pDst += processedLen;
        dataLen -= processedLen;
     }
     #endif
  
     for(; dataLen>0; dataLen-=MBS_SMS4, pSrc+=MBS_SMS4, pDst+=MBS_SMS4) {
        Ipp32u tmp[MBS_SMS4/sizeof(ipp32u)];
  
        cpSMS4_Cipher((Ipp8u*)tmp, (Ipp8u*)pSrc, pRoundKeys);
  
        tmp[0] ^= iv[0];
        tmp[1] ^= iv[1];
        tmp[2] ^= iv[2];
        tmp[3] ^= iv[3];
  
        iv[0] = ((Ipp32u*)pSrc)[0];
        iv[1] = ((Ipp32u*)pSrc)[1];
        iv[2] = ((Ipp32u*)pSrc)[2];
        iv[3] = ((Ipp32u*)pSrc)[3];
  
        CopyBlock16(tmp, pDst);
     }
  }
  
  #endif /* #if !defined _PCP_SMS4_DECRYPT_CBC_H */
  