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网上找到的des对称加密解密的代码，自己只是做个备份保存，方便以后用到的时候过来复制一下。

#include <iostream>
#include <vector>
#include <string.h>
#include "openssl/des.h"
using namespace std;

// ---- des对称加解密 ---- //  
// 加密 ecb模式  
std::string des_encrypt(const std::string &clearText, const std::string &key)
{
	std::string cipherText; // 密文

	DES_cblock keyEncrypt;
	memset(keyEncrypt, 0, 8);

	// 构造补齐后的密钥  
	if (key.length() <= 8)
		memcpy(keyEncrypt, key.c_str(), key.length());
	else
		memcpy(keyEncrypt, key.c_str(), 8);

	// 密钥置换  
	DES_key_schedule keySchedule;
	DES_set_key_unchecked(&keyEncrypt, &keySchedule);

	// 循环加密，每8字节一次  
	const_DES_cblock inputText;
	DES_cblock outputText;
	std::vector<unsigned char> vecCiphertext;
	unsigned char tmp[8];

	for (int i = 0; i < clearText.length() / 8; i++)
	{
		memcpy(inputText, clearText.c_str() + i * 8, 8);
		DES_ecb_encrypt(&inputText, &outputText, &keySchedule, DES_ENCRYPT);
		memcpy(tmp, outputText, 8);

		for (int j = 0; j < 8; j++)
			vecCiphertext.push_back(tmp[j]);
	}

	if (clearText.length() % 8 != 0)
	{
		int tmp1 = clearText.length() / 8 * 8;
		int tmp2 = clearText.length() - tmp1;
		memset(inputText, 0, 8);
		memcpy(inputText, clearText.c_str() + tmp1, tmp2);
		DES_ecb_encrypt(&inputText, &outputText, &keySchedule, DES_ENCRYPT);// 加密函数
		memcpy(tmp, outputText, 8);

		for (int j = 0; j < 8; j++)
			vecCiphertext.push_back(tmp[j]);
	}

	cipherText.clear();
	cipherText.assign(vecCiphertext.begin(), vecCiphertext.end());
	return cipherText;
}

// 解密 ecb模式  
std::string des_decrypt(const std::string &cipherText, const std::string &key)
{
	std::string clearText; // 明文  

	DES_cblock keyEncrypt;
	memset(keyEncrypt, 0, 8);

	if (key.length() <= 8)
		memcpy(keyEncrypt, key.c_str(), key.length());
	else
		memcpy(keyEncrypt, key.c_str(), 8);

	DES_key_schedule keySchedule;
	DES_set_key_unchecked(&keyEncrypt, &keySchedule);

	const_DES_cblock inputText;
	DES_cblock outputText;
	std::vector<unsigned char> vecCleartext;
	unsigned char tmp[8];

	for (int i = 0; i < cipherText.length() / 8; i++)
	{
		memcpy(inputText, cipherText.c_str() + i * 8, 8);
		DES_ecb_encrypt(&inputText, &outputText, &keySchedule, DES_DECRYPT);
		memcpy(tmp, outputText, 8);

		for (int j = 0; j < 8; j++)
			vecCleartext.push_back(tmp[j]);
	}

	if (cipherText.length() % 8 != 0)
	{
		int tmp1 = cipherText.length() / 8 * 8;
		int tmp2 = cipherText.length() - tmp1;
		memset(inputText, 0, 8);
		memcpy(inputText, cipherText.c_str() + tmp1, tmp2);
		DES_ecb_encrypt(&inputText, &outputText, &keySchedule, DES_DECRYPT);// 解密函数
		memcpy(tmp, outputText, 8);

		for (int j = 0; j < 8; j++)
			vecCleartext.push_back(tmp[j]);
	}

	clearText.clear();
	clearText.assign(vecCleartext.begin(), vecCleartext.end());

	return clearText;
}


int main()
{
	string srcText = "Hello, this is an example";
	string desKey = "12345";
	string encryptText = des_encrypt(srcText, desKey);
	string decryptText = des_decrypt(encryptText, desKey);
	std::cout << "加密字符： " << encryptText.size() << std::endl;
	std::cout << "解密字符： " << decryptText.size() << std::endl;

	return 0;
}