openssl是一個加密庫，封裝了多個演算法，我們這裡使用的是DES演算法CBC模式。

一、準備OPENSSL的LINUX及C#庫

openssl專案地址：

C#下使用自帶庫

二、操作函式

using System.Text;
using System.IO;
using System.Security.Cryptography;

DES des_cbc = new DESCryptoServiceProvider();

public byte[] key_b;
public byte[] iv_b;

/// <summary>初始化</summary>
/// <param name="key">金鑰</param>
/// <param name="vi">向量</param>
public void init(string key, string vi)
{
    key_b = ASCIIEncoding.UTF8.GetBytes(key);  //金鑰  
    iv_b = ASCIIEncoding.UTF8.GetBytes(vi);   //初始化向量  
    des_cbc.Mode = CipherMode.CBC;
    des_cbc.Padding = PaddingMode.Zeros;
}

/// <summary>DES加密CBC模式0補齊</summary>
/// <param name="input">明文</param>
public byte[] ecrypt(byte[] input)
{
    MemoryStream ms = new MemoryStream();
    CryptoStream cs = new CryptoStream(ms, des_cbc.CreateEncryptor(key_b, iv_b), CryptoStreamMode.Write);
    cs.Write(input, 0, input.Length);
    cs.Close();
    byte[] ciphertext = ms.ToArray();
    return ciphertext;
}

/// <summary>DES解密CBC模式0補齊</summary>
/// <param name="input">明文</param>
public byte[] decrypt(byte[] input)
{
    MemoryStream ms = new MemoryStream();
    CryptoStream cs = new CryptoStream(ms, des_cbc.CreateDecryptor(key_b, iv_b), CryptoStreamMode.Write);
    cs.Write(input, 0, input.Length);
    cs.FlushFinalBlock();
    byte[] ciphertext = ms.ToArray();
    return ciphertext;
}
 

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

// DES-CBC加密方式  * 8位金鑰，加密內容8位補齊，補齊方式為填充0
int main(int argc, char *argv[])
{
	
	unsigned char buff[20]={"123412341234"};
	unsigned char encry_buff[20] ;
	int packet_len = strlen(buff);
	
	int i;
	int encry_len;
	memset(encry_buff,0,20);
		
	//金鑰
	DES_cblock KEY_DES = "
 
[email protected]";		
	//加密向量
	DES_cblock ivec = "thvn#&@@";	
	//解密向量
	DES_cblock ivec_de = "thvn#&@@";	
	DES_key_schedule schedule;			 	
	DES_set_key_unchecked((const_DES_cblock*)KEY_DES, &schedule);			 	
			 			 	
	encry_len = (strlen(buff)+7)/8*8;//長度		
		
	unsigned char *output=(char*)malloc(encry_len);	
	
	//加密
	memset(output,0,strlen(output));
	DES_ncbc_encrypt(buff, output, strlen(buff), &schedule, &ivec, DES_ENCRYPT);

	//解密
 	memset(buff,0,20);
 	DES_ncbc_encrypt(output, buff, strlen(output), &schedule, &ivec_de, DES_DECRYPT);

 	free(output);
 	return 0;	 	
}