#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <openssl/des.h>

/************************************************************************

** 本例采用：

** 3des-ecb加密方式；

** 24位密钥，不足24位的右补0x00；

** 加密内容8位补齐，补齐方式为：少1位补一个0x01,少2位补两个0x02,...

** 本身已8位对齐的，后面补八个0x08。

************************************************************************/

int main(void)

{

    int docontinue = 1;

    char *data = "hello world!"; /* 明文 */

    int data_len;

    int data_rest;

    unsigned char ch;

    unsigned char *src = NULL; /* 补齐后的明文 */

    unsigned char *dst = NULL; /* 解密后的明文 */

    int len;

    unsigned char tmp[8];

    unsigned char in[8];

    unsigned char out[8];

    char *k = "01234567899876543210"; /* 原始密钥 */

    int key_len;

    #define LEN_OF_KEY 24

    unsigned char key[LEN_OF_KEY]; /* 补齐后的密钥 */

    unsigned char block_key[9];

    DES_key_schedule ks,ks2,ks3;

    /* 构造补齐后的密钥 */

    key_len = strlen(k);

    memcpy(key, k, key_len);

    memset(key + key_len, 0x00, LEN_OF_KEY - key_len);

    /* 分析补齐明文所需空间及补齐填充数据 */

    data_len = strlen(data);

    data_rest = data_len % 8;

    len = data_len + (8 - data_rest);

    ch = 8 - data_rest;

    src = (unsigned char *)malloc(len);

    dst = (unsigned char *)malloc(len);

    if (NULL == src || NULL == dst)

    {

        docontinue = 0;

    }

    if (docontinue)

    {

        int count;

        int i;

        /* 构造补齐后的加密内容 */

        memset(src, 0, len);

        memcpy(src, data, data_len);

        memset(src + data_len, ch, 8 - data_rest);

        /* 密钥置换 */

        memset(block_key, 0, sizeof(block_key));

        memcpy(block_key, key + 0, 8);

        DES_set_key_unchecked((const_DES_cblock*)block_key, &ks);

        memcpy(block_key, key + 8, 8);

        DES_set_key_unchecked((const_DES_cblock*)block_key, &ks2);

        memcpy(block_key, key + 16, 8);

        DES_set_key_unchecked((const_DES_cblock*)block_key, &ks3);

        printf("before encrypt:\n");

        for (i = 0; i < len; i++)

        {

            printf("0x%.2X ", *(src + i));

        }

        printf("\n");

        /* 循环加密/解密，每8字节一次 */

        count = len / 8;

        for (i = 0; i < count; i++)

        {

            memset(tmp, 0, 8);

            memset(in, 0, 8);

            memset(out, 0, 8);

            memcpy(tmp, src + 8 * i, 8);

            /* 加密 */

            DES_ecb3_encrypt((const_DES_cblock*)tmp, (DES_cblock*)in, &ks, &ks2, &ks3, DES_ENCRYPT);

            /* 解密 */

            DES_ecb3_encrypt((const_DES_cblock*)in, (DES_cblock*)out, &ks, &ks2, &ks3, DES_DECRYPT);

            /* 将解密的内容拷贝到解密后的明文 */

            memcpy(dst + 8 * i, out, 8);

        }

        printf("after decrypt :\n");

        for (i = 0; i < len; i++)

        {

            printf("0x%.2X ", *(dst + i));

        }

        printf("\n");

    }

    if (NULL != src)

    {

        free(src);

        src = NULL;

    }

    if (NULL != dst)

    {

        free(dst);

        dst = NULL;

    }

    return 0;

}