ofbimpl.c

voltage 公司提供的一个开发Ibe的工具包

/* Copyright 2003-2004, Voltage Security, all rights reserved.
 */
#include "vibecrypto.h"
#include "environment.h"
#include "base.h"
#include "libctx.h"
#include "algobj.h"
#include "cipher.h"
#include "block.h"
#include "ofb.h"
#include "errorctx.h"

int OFBEncryptInit (
   VoltAlgorithmObject *algObj,
   VoltKeyObject *keyObj
   )
{
  int status;
  VoltLibCtx *libCtx = (VoltLibCtx *)(algObj->voltObject.libraryCtx);
  VoltCipherClassCtx *cipherCtx = (VoltCipherClassCtx *)(algObj->classCtx);
  VoltBlockCipherCtx *blockCtx =
    (VoltBlockCipherCtx *)(cipherCtx->localCipherCtx);
  VoltOFBCtx *ofbCtx = (VoltOFBCtx *)(blockCtx->feedbackCtx);
  VOLT_DECLARE_FNCT_LINE (fnctLine)

  do
  {
    /* Copy the initVector.
     */
    Z2Memcpy (
      ofbCtx->feedCtx.xorVector, ofbCtx->feedCtx.initVector,
      ofbCtx->feedCtx.blockSize);
    ofbCtx->xorUsed = ofbCtx->feedCtx.blockSize;

    /* Call the underlying algorithm's Init.
     */
    VOLT_SET_FNCT_LINE (fnctLine)
    status = ofbCtx->AlgEncryptInit (algObj, keyObj);

  } while (0);

  VOLT_LOG_ERROR_COMPARE (
    status, algObj->voltObject.libraryCtx, status, 0, fnctLine,
    "OFBEncryptInit", (char *)0)

  return (status);
}

int OFBEncryptUpdate (
   VoltAlgorithmObject *algObj,
   VtRandomObject random,
   unsigned char *dataToEncrypt,
   unsigned int dataToEncryptLen,
   unsigned char *encryptedData
   )
{
  unsigned int index, dataLen;
  VoltCipherClassCtx *cipherCtx = (VoltCipherClassCtx *)(algObj->classCtx);
  VoltBlockCipherCtx *blockCtx =
    (VoltBlockCipherCtx *)(cipherCtx->localCipherCtx);
  VoltOFBCtx *ofbCtx = (VoltOFBCtx *)(blockCtx->feedbackCtx);

  /* If we have some unused bytes in the XOR vector, use them.
   */
  if (ofbCtx->xorUsed < ofbCtx->feedCtx.blockSize)
  {
    /* Are there enough dataToEncrypt bytes to finish out the block of
     * XOR bytes we have available?
     */
    dataLen = ofbCtx->feedCtx.blockSize - ofbCtx->xorUsed;
    if (dataToEncryptLen < dataLen)
      dataLen = dataToEncryptLen;
    for (index = ofbCtx->xorUsed; index < (ofbCtx->xorUsed + dataLen) ; ++index)
    {
      /* Encrypted data is the input XOR'd with a byte from the XOR
       * vector.
       */
      *encryptedData = *dataToEncrypt ^ ofbCtx->feedCtx.xorVector[index];
      dataToEncrypt++;
      encryptedData++;
    }
    dataToEncryptLen -= dataLen;
    ofbCtx->xorUsed += dataLen;
  }

  /* So long as we have blocks, operate on them.
   */
  while (dataToEncryptLen >= ofbCtx->feedCtx.blockSize)
  {
    /* Encrypt the xorVector to get the next XOR vector.
     */
    ofbCtx->AlgEncryptUpdate (
      algObj, random, ofbCtx->feedCtx.xorVector, ofbCtx->feedCtx.blockSize,
      ofbCtx->feedCtx.xorVector);

    /* XOR each byte of input with the XOR vector. This will be the
     * ciphertext.
     */
    for (index = 0; index < ofbCtx->feedCtx.blockSize; ++index)
      encryptedData[index] =
        ofbCtx->feedCtx.xorVector[index] ^ dataToEncrypt[index];

    dataToEncrypt += ofbCtx->feedCtx.blockSize;
    encryptedData += ofbCtx->feedCtx.blockSize;
    dataToEncryptLen -= ofbCtx->feedCtx.blockSize;
  }

  /* After processing full blocks, if there's no more input, we're done.
   */
  if (dataToEncryptLen == 0)
    return (0);

  /* We have some leftovers, create the XOR vector.
   */
  ofbCtx->AlgEncryptUpdate (
    algObj, random, ofbCtx->feedCtx.xorVector, ofbCtx->feedCtx.blockSize,
    ofbCtx->feedCtx.xorVector);

  for (index = 0; index < dataToEncryptLen; ++index)
    encryptedData[index] =
      dataToEncrypt[index] ^ ofbCtx->feedCtx.xorVector[index];

  ofbCtx->xorUsed = dataToEncryptLen;

  return (0);
}