[JAVA] TCP/IP 데이터통신 데이터 암호화 서버,클라이언트

Java에서 암호화 및 암호 해독을 위한 프레임워크를 제공하는 javax.crypto 패키지를 사용하여 이전 예제에 암호화를 추가할 수 있습니다. 다음은 AES 알고리즘을 사용하여 데이터 암호화를 추가하는 서버 및 클라이언트의 업데이트된 예입니다

Server

import java.io.*;
import java.net.*;
import javax.crypto.*;
import javax.crypto.spec.*;
import java.security.*;
import java.util.Base64;

class TCPServer {
    public static void main(String argv[]) throws Exception {
        ServerSocket welcomeSocket = new ServerSocket(6789);
        while (true) {
            Socket connectionSocket = welcomeSocket.accept();
            ClientThread ct = new ClientThread(connectionSocket);
            ct.start();
        }
    }
}

class ClientThread extends Thread {
    Socket connectionSocket;
    SecretKeySpec secretKey;
    Cipher cipher;

    public ClientThread(Socket socket) {
        this.connectionSocket = socket;
        try {
            KeyGenerator keyGenerator = KeyGenerator.getInstance("AES");
            keyGenerator.init(128);
            secretKey = new SecretKeySpec(keyGenerator.generateKey().getEncoded(), "AES");
            cipher = Cipher.getInstance("AES");
        } catch (NoSuchAlgorithmException | NoSuchPaddingException e) {
            System.out.println("Encryption error: " + e.getMessage());
        }
    }

    public void run() {
        try {
            BufferedReader inFromClient = new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));
            DataOutputStream outToClient = new DataOutputStream(connectionSocket.getOutputStream());
            while (true) {
                cipher.init(Cipher.DECRYPT_MODE, secretKey);
                byte[] decryptedMessage = Base64.getDecoder().decode(inFromClient.readLine());
                String clientSentence = new String(cipher.doFinal(decryptedMessage));
                System.out.println("Received: " + clientSentence);
                cipher.init(Cipher.ENCRYPT_MODE, secretKey);
                byte[] encryptedMessage = cipher.doFinal(clientSentence.toUpperCase().getBytes());
                String capitalizedSentence = Base64.getEncoder().encodeToString(encryptedMessage) + '\n';
                outToClient.writeBytes(capitalizedSentence);
            }
        } catch (IOException | InvalidKeyException | IllegalBlockSizeException | BadPaddingException e) {
            System.out.println("Connection lost: " + e.getMessage());
        }
    }
}

 

Client

import java.io.*;
import java.net.*;
import javax.crypto.*;
import javax.crypto.spec.*;
import java.security.*;
import java.util.Base64;

class TCPClient {
    public static void main(String argv[]) throws Exception {
        String sentence;
        String modifiedSentence;
        BufferedReader inFromUser = new BufferedReader(new InputStreamReader(System.in));
        Socket clientSocket = new Socket("hostname", 6789);
        DataOutputStream outToServer = new DataOutputStream(clientSocket.getOutputStream());
        BufferedReader inFromServer = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
        SecretKeySpec secretKey;
        Cipher cipher;
        try {
            KeyGenerator keyGenerator = KeyGenerator.getInstance("AES");
            keyGenerator.init(128);
            secretKey = new SecretKeySpec(keyGenerator.generateKey().getEncoded(), "AES");
            cipher = Cipher.getInstance("AES");
        } catch (NoSuchAlgorithmException | NoSuchPaddingException e) {
            System.out.println("Encryption error: " + e.getMessage());
            return;
        }
        while (true) {
            System.out.print("Enter a sentence: ");
            sentence = inFromUser.readLine();
            cipher.init(Cipher.ENCRYPT_MODE, secretKey);
            byte[] encryptedMessage = cipher.doFinal(sentence.getBytes());
            String encryptedSentence = Base64.getEncoder().encodeToString(encryptedMessage) + '\n';
            outToServer.writeBytes(encryptedSentence);
            cipher.init(Cipher.DECRYPT_MODE, secretKey);
            byte[] decryptedMessage = Base64.getDecoder().decode(inFromServer.readLine());
            modifiedSentence = new String(cipher.doFinal(decryptedMessage));
            System.out.println("From server: " + modifiedSentence);
        }
    }
}