OpenSSL加解密

http://www.caole.net/diary/des.html

Table of Contents

• OpenSSL - DES
  • Summary
  • DES使用的例子
  • 另一个带注释的例子
  • 另一段Code:

OpenSSL - DES

 

Summary

This library contains a fast implementation of the DES encryption algorithm.

There are two phases to the use of DES encryption.

• The first is the generation of a DES_keyschedule from a key,
• The second is the actual encryption. A DES key is of type DES_cblock. This type is consists of 8 bytes with odd parity. The least significant bit in each byte is the parity bit. The key schedule is an expanded form of the key; it is used to speed the encryption process.

DES使用的例子

/**//*
gcc -o des-basic des-basic.c -lcrypto
*/

#include <stdio.h>
#include <openssl/des.h>

int main(int argc,char **argv)
{
    DES_cblock key;
    /**//* DES_random_key(&key); */ /**//* generate a random key */
    DES_string_to_key("pass", &key);

    DES_key_schedule schedule;
    DES_set_key_checked(&key, &schedule); 

    const_DES_cblock input = "hehehe";
    DES_cblock output;

    printf("cleartext:%s ", input);

    DES_ecb_encrypt(&input, &output, &schedule, DES_ENCRYPT);
    printf("Encrypted! ");

    printf("ciphertext:");
    int i;
    for (i = 0; i < sizeof(input); i++)
         printf("%02x", output[i]);
    printf(" ");

    DES_ecb_encrypt(&output, &input, &schedule, DES_DECRYPT);
    printf("Decrypted! ");
    printf("cleartext:%s ", input);

    return 0;
} 

另一个带注释的例子

// DES encrypt with OpenSSL support
// g++ crypt.cc -lssl -o crypt

#include <openssl/des.h>;
#include <iostream>;

int main(int argc, char** argv)
{
   try
   {
      std::string keystring("this is my key");// 初始化key(密钥)
      DES_cblock key[1];   //具体是什么?不知道也一样可以用
      DES_key_schedule key_schedule;   //字面意思是密码表

      if (NULL != argv[1])
         keystring.assign(argv[1]);//如果命令行指定了key,那么就用指定的

      // 生成一个 key
      DES_string_to_key(keystring.c_str(), key);
      if (DES_set_key_checked(key, &key_schedule) != 0)
         throw "DES_set_key_schedule";

      unsigned char input[] = "this is a text being encrypted by openssl";//需要加密的字符串
      size_t len = (sizeof(input)+7)/8 * 8;  
      unsigned char *output = new unsigned char[len+1];
       //加密以后的内容怎么分配内存,照上面这两步走就是了
       //错了就干掉贴代码的人:mrgreen:
      DES_cblock ivec;  
       //照这个搞就是了,用别人的代码不一定要知道所由的细节是为什么

      // 加密
      memset((char*)&ivec, 0, sizeof(ivec));//ivec清0
      DES_ncbc_encrypt(input, output, sizeof(input), &key_schedule, &ivec, 1);//这里就进行加密了
      std::cout << input << std::endl;

      //输出加密以后的内容
      for (int i = 0; i < len; ++i)
         printf("%02x", output[i]);
      std::cout << std::endl;

      // 解密
      memset((char*)&ivec, 0, sizeof(ivec));
      DES_ncbc_encrypt(output, input, len, &key_schedule, &ivec, 0);
      std::cout << input << std::endl;

      delete[] output;
   }
   catch(const char* errstr)   //对抛出异常的处理
   {
      std::cerr << errstr << std::endl;
      return EXIT_FAILURE;
   }

   return EXIT_SUCCESS;

另一段Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <openssl/des.h>

#define LEN_OF_KEY 24

int main(void)
{
    char tmp_str[512];
    int tmp_len;

    int docontinue = 1;
    unsigned char *data = "530160";
    int data_len;
    int data_rest;
    unsigned char ch;

    unsigned char *src = NULL;
    unsigned char *dst = NULL;
    int len;
    unsigned char tmp[8];
    unsigned char in[8];
    unsigned char out[8];

    char *k = "12345678901234567890";
    int key_len;
    unsigned char key[LEN_OF_KEY];
    unsigned char block_key[9];
    DES_key_schedule ks,ks2,ks3;

    key_len = strlen(k);
    memcpy(key, k, key_len);
    memset(key + key_len, 0x00, LEN_OF_KEY - key_len);

    data_len = strlen(data);
    data_rest = data_len % 8;
    len = data_len + (8 - data_rest);
    ch = 8 - data_rest;

    src = malloc(len);
    dst = malloc(len);
    if (NULL == src || NULL == dst)
    {
        docontinue = 0;
    }
    if (docontinue)
    {
        int count;
        int i, j;

        memset(src, 0, len);
        memcpy(src, data, data_len);
        memset(src + data_len, ch, 8 - data_rest);

        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:");
        for (i = 0; i < len; i++)
        {
            printf("0x%.2X ", *(src + i));
        }
        printf("
");

        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);

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

            for(j = 0; j < sizeof(in); j++){
                printf("%02x", in[j]);
            }
            printf("
");

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


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

        printf("after decrypt :");
        for (i = 0; i < len; i++)
        {
            printf("0x%.2X ", *(dst + i));
        }

        printf("[%s]
", dst);
    }

    if (NULL != src)
    {
        free(src);
        src = NULL;
    }
    if (NULL != dst)
    {
        free(dst);
        dst = NULL;
    }

    return 0;
}

Author: Le Cao

Date: 2010-10-12 18:19:41 CST

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