技巧：用Java语言实现对称加密实例详解

//从密钥文件中读密钥

   SecretKey key=null;

   try

   {

   //从密钥文件读取密钥

ObjectInputStream keyFile=new ObjectInputStream(

     new FileInputStream("c:\\安全文件\\"+misClass.username+
"\\对称\\对称密钥\\yhb.des"));

    key=(SecretKey)keyFile.readObject();

    keyFile.close();

    }

    catch(FileNotFoundException ey1)

    {

    System.out.println("Error when read keyFile");

    System.exit(0);

    }

    catch(Exception ey2)

    {

    System.out.println("error when read the keyFile");

    System.exit(0);

    }

    //用key产生Cipher

    Cipher cipher=null;

    try

{

//加密要用Cipher来实现

cipher=Cipher.getInstance("DES");

//设置加密模式

     cipher.init(Cipher.ENCRYPT_MODE,key);

     }catch(Exception ey3)

     {

     System.out.println("Error when create the cipher");

     System.exit(0);

     }

     //从对话框中取得要加密的文件

     File file=new File(dirstring,string1);

     String filename=file.getName();

     //读入并加密文件

     try

{

//输入流

BufferedInputStream in=new BufferedInputStream(new FileInputStream(file));

//输出流

CipherOutputStream out=new CipherOutputStream(new BufferedOutputStream(

new FileOutputStream("c:\\安全文件\\文件\\"+filename+".yhb")),cipher);

      int i;

        do{

        i=in.read();

        if(i!=-1) out.write(i);

         }while(i!=-1);

      in.close();

      out.close();

      }

      catch(Exception ey5)

      {

      System.out.println("Error when encrypt the file");

      System.exit(0);

      }