懂了！国际算法体系对称算法DES原理

@Test
public void caesarCipher() {
    String text = "love was growing in eyes";  //明文
        int key = 3; //秘钥
        String cipher = encryptCaesarCipher(text, key); //密文
        System.out.println(cipher);
}
//凯撒密码加密算法
private String encryptCaesarCipher(String text, int key) {
    char[] chars = text.toCharArray();
    for(int i=0; i<chars.length; i++) {
        if(chars[i] != ' ') {
            chars[i] = (char)(chars[i]+key);
        }
        //如果超过了26个字母，则减去26
        if(chars[i]>122) {
            chars[i] = (char)(chars[i]-26);
        }
    }
    return new String(chars);
}

@Test
public void desCiper() throws Exception{
    String key = "12345678";
    String text = "我知道我是任性很任性，伤透了你的心";  //明文
        String cipher = encryptDesCipher(text, key); //密文
        System.out.println(cipher);
    text = decryptDesCipher(cipher, key);  //明文
         System.out.println(text);
}
//DES加密算法
private String encryptDesCipher(String text, String origKey) throws Exception{
    Key key = new SecretKeySpec(origKey.getBytes(), "DES");
    Cipher cipher = Cipher.getInstance("DES");
    cipher.init(Cipher.ENCRYPT_MODE, key);
    return Base64.encode(cipher.doFinal(text.getBytes()));
}
//DES加密算法
private String decryptDesCipher(String text, String origKey) throws Exception{
    Key key = new SecretKeySpec(origKey.getBytes(), "DES");
    Cipher cipher = Cipher.getInstance("DES");
    cipher.init(Cipher.DECRYPT_MODE, key);
    return new String(cipher.doFinal(Base64.decode(text)));
}

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@Test
public void client() throws Exception {
    int i = 1;
    while (i <= 2) {
        Socket socket = new Socket("127.0.0.1", 520);
        //向服务器端第一次发送字符串
        OutputStream netOut = socket.getOutputStream();
        InputStream io = socket.getInputStream();
        String msg = i == 1 ? "客户端：我知道我是任性太任性，伤透了你的心。我是追梦的人，追一生的缘分。":
        "客户端：我愿意嫁给你，你却不能答应我。";
        System.out.println(msg);
        netOut.write(encryptDesCipher(msg.getBytes(), "12345678"));
        netOut.flush();
        byte[] bytes = new byte[i==1?104:64];
        io.read(bytes);
        String response = new String(decryptDesCipher(bytes,"12345678"));
        System.out.println(response);
        netOut.close();
        io.close();
        socket.close();
        i++;
    }
}
@Test
public void server() throws Exception {
    ServerSocket serverSocket = new ServerSocket(520);
    int i = 1;
    while (i <= 2) {
        String msg = i == 1 ? "服务端：我知道你是任性太任性，伤透了我的心。同是追梦的人，难舍难分。" :
                "服务端：你愿意嫁给我，我却不能向你承诺。";
        Socket socket = serverSocket.accept();
        InputStream io = socket.getInputStream();
        byte[] bytes = new byte[i==1?112:64];
        io.read(bytes);
        System.out.println(new String(decryptDesCipher(bytes,"12345678")));
        OutputStream os = socket.getOutputStream();
        System.out.println(msg);
        byte[] outBytes = encryptDesCipher(msg.getBytes(), "12345678");
        os.write(outBytes);
        os.flush();
        os.close();
        io.close();
        i++;
    }
}

//DES加密算法
private byte[] encryptDesCipher(byte[] text, String origKey) throws Exception {
    Key key = new SecretKeySpec(origKey.getBytes(), "DES");
    Cipher cipher = Cipher.getInstance("DES");
    cipher.init(Cipher.ENCRYPT_MODE, key);
    return cipher.doFinal(text);
}
//DES加密算法
private byte[] decryptDesCipher(byte[] text, String origKey) throws Exception {
    Key key = new SecretKeySpec(origKey.getBytes(), "DES");
    Cipher cipher = Cipher.getInstance("DES");
    cipher.init(Cipher.DECRYPT_MODE, key);
    return cipher.doFinal(text);
}