OpenSSL - 文件和字符MD5加密实现

OpenSSL安装：

1.github下载最新的OpenSSL：https://github.com/openssl/openssl

2.在linux解压压缩包

3.安装OpenSSL

 ./config  --prefix=/usr/local --openssldir=/usr/local/ssl
 make && make install
 ./config shared --prefix=/usr/local --openssldir=/usr/local/ssl
 make clean
 make && make install

4.用ln将需要的so文件链接到/usr/lib或者/lib这两个默认的目录下面

 ln -s /where/you/install/lib/*.so /usr/lib
 sudo ldconfig

openssl MD5接口：

 int MD5_Init(MD5_CTX *c);
 //初始化MD5上下文结构

 int MD5_Update(MD5_CTX *c, const void *data, size_t len);
 //刷新MD5，将文件连续数据分片放入进行MD5刷新。

 int MD5_Final(unsigned char *md, MD5_CTX *c);
 //产生最终的MD5数据

 unsigned char *MD5(const unsigned char *d, size_t n, unsigned char *md);
 //直接产生字符串的MD5

代码实现：

 #include <iostream>
 #include <fstream>
 #include <iomanip>
 #include <string>
 #include <openssl/md5.h>

 using namespace std;

 #define MAXDATABUFF 1024
 #define MD5LENTH 16

 int main(int arc,char *arv[])
 {
     string strFilePath = arv[];
     ifstream ifile(strFilePath.c_str(),ios::in|ios::binary);    //打开文件
     unsigned char MD5result[MD5LENTH];
     do
     {
         if (ifile.fail())   //打开失败不做文件MD5
         {
             cout<<"open file failure!so only display string MD5!"<<endl;
             break;
         }
         MD5_CTX md5_ctx;
         MD5_Init(&md5_ctx);

         char DataBuff[MAXDATABUFF];
         while(!ifile.eof())
         {
             ifile.read(DataBuff,MAXDATABUFF);   //读文件
             int length = ifile.gcount();
             if(length)
             {
                 MD5_Update(&md5_ctx,DataBuff,length);   //将当前文件块加入并更新MD5
             }
         }
         MD5_Final(MD5result,&md5_ctx);  //获取MD5
         cout<<"file MD5:"<<endl;
         for(int i = ; i < MD5LENTH; i++)  //将MD5以16进制输出
             cout<< hex <<(int)MD5result[i];
         cout<<endl;
     }while(false); 

     MD5((const unsigned char*)strFilePath.c_str(),strFilePath.size(),MD5result);    //获取字符串MD5
     cout<<"string MD5:"<<endl;
     for(int i = ; i < MD5LENTH; i++)
         cout << hex << (int)MD5result[i];
     cout<<endl;
     return ;
 }

SConstruct：

Program('md5','md5.cpp',LIBS = ['ssl','crypto'])

测试结果与命令行比较：