OpenSSL - DES

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 24int 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("\n");        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("\n");            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]\n", 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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