cbc.c

掌握如何用C来实现各种算法

/*****************************************************************************
*                                                                            *
*  --------------------------------- cbc.c --------------------------------  *
*                                                                            *
*****************************************************************************/

#include <stdlib.h>

#include "bit.h"
#include "cbc.h"
#include "encrypt.h"

/*****************************************************************************
*                                                                            *
*  ----------------------------- cbc_encipher -----------------------------  *
*                                                                            *
*****************************************************************************/

void cbc_encipher(const unsigned char *plaintext, unsigned char *ciphertext,
   const unsigned char *key, int size) {

unsigned char      temp[8];

int                i;

/*****************************************************************************
*                                                                            *
*  Encipher the initialization vector.                                       *
*                                                                            *
*****************************************************************************/

des_encipher(&plaintext[0], &ciphertext[0], key);

/*****************************************************************************
*                                                                            *
*  Encipher the buffer using DES in CBC mode.                                *
*                                                                            *
*****************************************************************************/

i = 8;

while (i < size) {

   bit_xor(&plaintext[i], &ciphertext[i - 8], temp, 64);
   des_encipher(temp, &ciphertext[i], NULL);
   i = i + 8;

}

return;

}

/*****************************************************************************
*                                                                            *
*  ----------------------------- cbc_decipher -----------------------------  *
*                                                                            *
*****************************************************************************/

void cbc_decipher(const unsigned char *ciphertext, unsigned char *plaintext,
   const unsigned char *key, int size) {

unsigned char      temp[8];

int                i;

/*****************************************************************************
*                                                                            *
*  Decipher the initialization vector.                                       *
*                                                                            *
*****************************************************************************/

des_decipher(&ciphertext[0], &plaintext[0], key);

/*****************************************************************************
*                                                                            *
*  Decipher the buffer using DES in CBC mode.                                *
*                                                                            *
*****************************************************************************/

i = 8;

while (i < size) {

   des_decipher(&ciphertext[i], temp, NULL);
   bit_xor(&ciphertext[i - 8], temp, &plaintext[i], 64);
   i = i + 8;

}

return;

}