encfile.cpp

aes和des加密的小程序：可以加密文件

/*
 * @(#)encfile.cpp          2006-06-18 01:44:44
 * Copyright 2006 HUST Software School. All rights reserved.
 * Author: 翟黎 软件0309 01012003026327 Email:[e-mail]
 */

#include "stdafx.h"

/* #include <stdlib.h> */
#include <stdio.h>
/* #include <time.h> */

#include "aes.h"

//定义文件加密的块大小(也就是加密算法输入的块大小)
#define BLOCK_SIZE 16


//AES文件加密函数
/*
    文件加密采用ECB模式,也就是电话簿模式,别的模式有待实现
    最后在文件的尾部写入加密文件的大小(当然也是加密过的数据)
    @param fr  需要加密的文件
    @param fw  加密后输出的文件
    @param key 加密所需的密钥
*/
int AES_file_encrypt(const char* fr, const char* fw, const byte key[16])
{
    byte buf[BLOCK_SIZE];
    FILE *fp_r, *fp_w;
    int i, r_size;

    if ((fp_r = fopen(fr, "rb")) == NULL) {
        fprintf(stderr, "Error reading file.");
        return 1;
    }
    if ((fp_w = fopen(fw, "wb")) == NULL) {
        fprintf(stderr, "Error reading file.");
        fclose(fp_r);
        return 1;
    }

    //读入初始的文件块
    r_size = fread(buf, sizeof(byte), BLOCK_SIZE, fp_r);
    while (r_size == BLOCK_SIZE) {
        //加密文件快
        AES_encrypt(buf, buf, key);
        //写入到文件
        fwrite(buf, sizeof(byte), BLOCK_SIZE, fp_w);
        //读入下一个块
        r_size = fread(buf, sizeof(byte), BLOCK_SIZE, fp_r);
    }

    //如果不是文件结束,返回错误值
    if (!feof(fp_r)) {
        fprintf(stderr, "Error reading file in feof.");
        fclose(fp_r);
        fclose(fp_w);
        return 1;
    }

    //写入最后一块,不够16位的补零
    for (i = r_size; i < BLOCK_SIZE; i++)
        buf[i] = 0;
    AES_encrypt(buf, buf, key);
    fwrite(buf, sizeof(byte), BLOCK_SIZE, fp_w);

    *((int *)buf) = ftell(fp_r);
    AES_encrypt(buf, buf, key);
    //写入文件大小,放在最后
    fwrite(buf, sizeof(byte), BLOCK_SIZE, fp_w);

/*     for (i = 0; i < BLOCK_SIZE; i++) */
/*         printf("%02x ", buf[i]); */
/*     printf("\n"); */
/*         printf("last count:%d\n", r_size); */

    fclose(fp_r);
    fclose(fp_w);

    return 0;
}

//AES文件解密密函数
/*
    文件解密密同样采用ECB模式
    @param fr  需要解密的文件
    @param fw  解密后输出的文件
    @param key 解密所需的密钥
*/
int AES_file_decrypt(const char* fr, const char* fw, const byte key[16])
{
    byte buf1[BLOCK_SIZE], buf2[BLOCK_SIZE], buf3[BLOCK_SIZE],
        *p, *q, *r, *t;
    FILE *fp_r, *fp_w;
    int r_size, diff;

    if ((fp_r = fopen(fr, "rb")) == NULL) {
        fprintf(stderr, "Error reading file.");
        return 1;
    }
    if ((fp_w = fopen(fw, "wb")) == NULL) {
        fprintf(stderr, "Error reading file.");
        fclose(fp_r);
        return 1;
    }

    p = buf1, q = buf2, r = buf3;
    r_size = fread(p, sizeof(byte), BLOCK_SIZE, fp_r);

    //读入初始的两块
    if (r_size != BLOCK_SIZE) {
        fprintf(stderr, "Decrypt file failed");
        fclose(fp_r);
        fclose(fp_w);
        return 1;
    }
    r_size = fread(q, sizeof(byte), BLOCK_SIZE, fp_r);
    if (r_size != BLOCK_SIZE) {
        fprintf(stderr, "Decrypt file failed");
        fclose(fp_r);
        fclose(fp_w);
        return 1;
    }
    r_size = fread(r, sizeof(byte), BLOCK_SIZE, fp_r);

    while (r_size == BLOCK_SIZE) {
        //先解密然后再写入
        AES_decrypt(p, p, key);
        fwrite(p, sizeof(byte), BLOCK_SIZE, fp_w);
        t = p; p = q; q = r; r = t;
        //读入下一块
        r_size = fread(r, sizeof(byte), BLOCK_SIZE, fp_r);

/*         for (i = 0; i < BLOCK_SIZE; i++) */
/*             printf("%02x ", p[i]); */
/*         printf("\n"); */
/*         for (i = 0; i < BLOCK_SIZE; i++) */
/*             printf("%02x ", q[i]); */
/*         printf("\n"); */
/*         for (i = 0; i < BLOCK_SIZE; i++) */
/*             printf("%02x ", r[i]); */
/*         printf("\n"); */
    }

    if (!feof(fp_r)) {
        fprintf(stderr, "Error reading file in feof.");
        fclose(fp_r);
        fclose(fp_w);
        return 1;
    }

    //解密最后的两块,最后一块放的是加密前文件的大小
    AES_decrypt(p, p, key);
    AES_decrypt(q, q, key);

    //计算倒数第二块的大小,并写入
    diff = 32 + *(int *)q - ftell(fp_r);
    if (diff > 0 && diff < 16)
        fwrite(p, sizeof(byte), diff, fp_w);

    fclose(fp_r);
    fclose(fp_w);

    return 0;
}

/* int main() */
/* { */
/*     byte ckey[] = {0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, */
/*                    0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f}; */

/*     clock_t start, finish; */
/*     double duration; */
/*     start = clock(); */

/*     //AES_file_encrypt("123.rar", "123.rar.enc", ckey); */
/*     AES_file_decrypt("123.rar.enc", "123.rar.dec", ckey); */

/* /\*     AES_file_encrypt("aes.o", "aes.o.enc", ckey); *\/ */
/* /\*     AES_file_decrypt("aes.o.enc", "aes.o.dec", ckey); *\/ */

/*     finish = clock(); */
/*     duration = (double)(finish - start) / CLOCKS_PER_SEC; */
/*     printf("%lf", duration); */

/*     return 0; */
/* } */