UINT4 inputBlock[2], work[2];
  unsigned int i;
  
  if (len % 8)
    return (RE_LEN);

  for (i = 0; i < len/8; i++)  {
    Pack (inputBlock, &input[8*i]);
        
    /* Chain if encrypting, and xor with whitener.
     */
    if (context->encrypt) {
      work[0] =
        inputBlock[0] ^ context->iv[0] ^ context->inputWhitener[0];
      work[1] =
        inputBlock[1] ^ context->iv[1] ^ context->inputWhitener[1];
    }
    else {
      work[0] = inputBlock[0] ^ context->outputWhitener[0];
      work[1] = inputBlock[1] ^ context->outputWhitener[1];         
    }

    DESFunction (work, context->subkeys);

    /* Xor with whitener, chain if decrypting, then update IV.
     */
    if (context->encrypt) {
      work[0] ^= context->outputWhitener[0];
      work[1] ^= context->outputWhitener[1];
      context->iv[0] = work[0];
      context->iv[1] = work[1];
    }
    else {
      work[0] ^= context->iv[0] ^ context->inputWhitener[0];
      work[1] ^= context->iv[1] ^ context->inputWhitener[1];
      context->iv[0] = inputBlock[0];
      context->iv[1] = inputBlock[1];
    }
    Unpack (&output[8*i], work);
  }
  
  /* Zeroize sensitive information.
   */
  R_memset ((POINTER)inputBlock, 0, sizeof (inputBlock));
  R_memset ((POINTER)work, 0, sizeof (work));
  
  return (0);
}

void DESX_CBCRestart (context)
DESX_CBC_CTX *context;
{
  /* Reset to the original IV */
  context->iv[0] = context->originalIV[0];
  context->iv[1] = context->originalIV[1];
}

/* Initialize context.  Caller must zeroize the context when finished.
 */
void DES3_CBCInit(context, key, iv, encrypt)
DES3_CBC_CTX *context;                                           /* context */
unsigned char key[24];                                               /* key */
unsigned char iv[8];                                 /* initializing vector */
int encrypt;                     /* encrypt flag (1 = encrypt, 0 = decrypt) */
{  
  /* Copy encrypt flag to context.
   */
  context->encrypt = encrypt;

  /* Pack initializing vector into context.
   */
  Pack (context->iv, iv);

  /* Save the IV for use in Restart */
  context->originalIV[0] = context->iv[0];
  context->originalIV[1] = context->iv[1];

  /* Precompute key schedules.
   */
  DESKey (context->subkeys[0], encrypt ? key : &key[16], encrypt);
  DESKey (context->subkeys[1], &key[8], !encrypt);
  DESKey (context->subkeys[2], encrypt ? &key[16] : key, encrypt);
}

int DES3_CBCUpdate (context, output, input, len)
DES3_CBC_CTX *context;                                           /* context */
unsigned char *output;                                      /* output block */
unsigned char *input;                                        /* input block */
unsigned int len;                      /* length of input and output blocks */
{
  UINT4 inputBlock[2], work[2];
  unsigned int i;
  
  if (len % 8)
    return (RE_LEN);

  for (i = 0; i < len/8; i++) {
    Pack (inputBlock, &input[8*i]);
        
    /* Chain if encrypting.
     */
    if (context->encrypt) {
      work[0] = inputBlock[0] ^ context->iv[0];
      work[1] = inputBlock[1] ^ context->iv[1];
    }
    else {
      work[0] = inputBlock[0];
      work[1] = inputBlock[1];         
    }

    DESFunction (work, context->subkeys[0]);
    DESFunction (work, context->subkeys[1]);
    DESFunction (work, context->subkeys[2]);

    /* Chain if decrypting, then update IV.
     */
    if (context->encrypt) {
      context->iv[0] = work[0];
      context->iv[1] = work[1];
    }
    else {
      work[0] ^= context->iv[0];
      work[1] ^= context->iv[1];
      context->iv[0] = inputBlock[0];
      context->iv[1] = inputBlock[1];
    }
    Unpack (&output[8*i], work);
  }
  
  /* Zeroize sensitive information.
   */
  R_memset ((POINTER)inputBlock, 0, sizeof (inputBlock));
  R_memset ((POINTER)work, 0, sizeof (work));
  
  return (0);
}

void DES3_CBCRestart (context)
DES3_CBC_CTX *context;
{
  /* Reset to the original IV */
  context->iv[0] = context->originalIV[0];
  context->iv[1] = context->originalIV[1];
}

static void Pack (into, outof)
UINT4 *into;
unsigned char *outof;
{
  *into    = (*outof++ & 0xffL) << 24;
  *into   |= (*outof++ & 0xffL) << 16;
  *into   |= (*outof++ & 0xffL) << 8;
  *into++ |= (*outof++ & 0xffL);
  *into    = (*outof++ & 0xffL) << 24;
  *into   |= (*outof++ & 0xffL) << 16;
  *into   |= (*outof++ & 0xffL) << 8;
  *into   |= (*outof   & 0xffL);
}

static void Unpack (into, outof)
unsigned char *into;
UINT4 *outof;
{
  *into++ = (unsigned char)((*outof >> 24) & 0xffL);
  *into++ = (unsigned char)((*outof >> 16) & 0xffL);
  *into++ = (unsigned char)((*outof >>  8) & 0xffL);
  *into++ = (unsigned char)( *outof++      & 0xffL);
  *into++ = (unsigned char)((*outof >> 24) & 0xffL);
  *into++ = (unsigned char)((*outof >> 16) & 0xffL);
  *into++ = (unsigned char)((*outof >>  8) & 0xffL);
  *into   = (unsigned char)( *outof        & 0xffL);
}

static void DESKey (subkeys, key, encrypt)
UINT4 subkeys[32];
unsigned char key[8];
int encrypt;
{
  UINT4 kn[32];
  int i, j, l, m, n;
  unsigned char pc1m[56], pcr[56];

  for (j = 0; j < 56; j++) {
    l = PC1[j];
    m = l & 07;
    pc1m[j] = (unsigned char)((key[l >> 3] & BYTE_BIT[m]) ? 1 : 0);
  }
  for (i = 0; i < 16; i++) {
    m = i << 1;
    n = m + 1;
    kn[m] = kn[n] = 0L;
    for (j = 0; j < 28; j++) {
      l = j + TOTAL_ROTATIONS[i];
      if (l < 28)
        pcr[j] = pc1m[l];
      else
        pcr[j] = pc1m[l - 28];
    }
    for (j = 28; j < 56; j++) {
      l = j + TOTAL_ROTATIONS[i];
      if (l < 56)
        pcr[j] = pc1m[l];
      else
        pcr[j] = pc1m[l - 28];
    }
    for (j = 0; j < 24; j++) {
      if (pcr[PC2[j]])
        kn[m] |= BIG_BYTE[j];
      if (pcr[PC2[j+24]])
        kn[n] |= BIG_BYTE[j];
    }
  }
  CookKey (subkeys, kn, encrypt);

  /* Zeroize sensitive information.
   */
  R_memset ((POINTER)pc1m, 0, sizeof (pc1m));
  R_memset ((POINTER)pcr, 0, sizeof (pcr));
  R_memset ((POINTER)kn, 0, sizeof (kn));
}

static void CookKey (subkeys, kn, encrypt)
UINT4 *subkeys;
UINT4 *kn;
int encrypt;
{
  UINT4 *cooked, *raw0, *raw1;
  int increment;
  unsigned int i;

  raw1 = kn;
  cooked = encrypt ? subkeys : &subkeys[30];
  increment = encrypt ? 1 : -3;

  for (i = 0; i < 16; i++, raw1++) {
    raw0 = raw1++;
    *cooked    = (*raw0 & 0x00fc0000L) << 6;
    *cooked   |= (*raw0 & 0x00000fc0L) << 10;
    *cooked   |= (*raw1 & 0x00fc0000L) >> 10;
    *cooked++ |= (*raw1 & 0x00000fc0L) >> 6;
    *cooked    = (*raw0 & 0x0003f000L) << 12;
    *cooked   |= (*raw0 & 0x0000003fL) << 16;
    *cooked   |= (*raw1 & 0x0003f000L) >> 4;
    *cooked   |= (*raw1 & 0x0000003fL);
    cooked += increment;
  }
}

static void DESFunction (block, subkeys)
UINT4 *block;
UINT4 *subkeys;
{
  register UINT4 fval, work, right, left;
  register int round;
  
  left = block[0];
  right = block[1];
  work = ((left >> 4) ^ right) & 0x0f0f0f0fL;
  right ^= work;
  left ^= (work << 4);
  work = ((left >> 16) ^ right) & 0x0000ffffL;
  right ^= work;
  left ^= (work << 16);
  work = ((right >> 2) ^ left) & 0x33333333L;
  left ^= work;
  right ^= (work << 2);
  work = ((right >> 8) ^ left) & 0x00ff00ffL;
  left ^= work;
  right ^= (work << 8);
  right = ((right << 1) | ((right >> 31) & 1L)) & 0xffffffffL;
  work = (left ^ right) & 0xaaaaaaaaL;
  left ^= work;
  right ^= work;
  left = ((left << 1) | ((left >> 31) & 1L)) & 0xffffffffL;
  
  for (round = 0; round < 8; round++) {
    work  = (right << 28) | (right >> 4);
    work ^= *subkeys++;
    fval  = SP7[ work        & 0x3fL];
    fval |= SP5[(work >>  8) & 0x3fL];
    fval |= SP3[(work >> 16) & 0x3fL];
    fval |= SP1[(work >> 24) & 0x3fL];
    work  = right ^ *subkeys++;
    fval |= SP8[ work        & 0x3fL];
    fval |= SP6[(work >>  8) & 0x3fL];
    fval |= SP4[(work >> 16) & 0x3fL];
    fval |= SP2[(work >> 24) & 0x3fL];
    left ^= fval;
    work  = (left << 28) | (left >> 4);
    work ^= *subkeys++;
    fval  = SP7[ work        & 0x3fL];
    fval |= SP5[(work >>  8) & 0x3fL];
    fval |= SP3[(work >> 16) & 0x3fL];
    fval |= SP1[(work >> 24) & 0x3fL];
    work  = left ^ *subkeys++;
    fval |= SP8[ work        & 0x3fL];
    fval |= SP6[(work >>  8) & 0x3fL];
    fval |= SP4[(work >> 16) & 0x3fL];
    fval |= SP2[(work >> 24) & 0x3fL];
    right ^= fval;
  }
  
  right = (right << 31) | (right >> 1);
  work = (left ^ right) & 0xaaaaaaaaL;
  left ^= work;
  right ^= work;
  left = (left << 31) | (left >> 1);
  work = ((left >> 8) ^ right) & 0x00ff00ffL;
  right ^= work;
  left ^= (work << 8);
  work = ((left >> 2) ^ right) & 0x33333333L;
  right ^= work;
  left ^= (work << 2);
  work = ((right >> 16) ^ left) & 0x0000ffffL;
  left ^= work;
  right ^= (work << 16);
  work = ((right >> 4) ^ left) & 0x0f0f0f0fL;
  left ^= work;
  right ^= (work << 4);
  *block++ = right;
  *block = left;
}