Input length must be multiple of 8 when decrypting with padded cipher

Question

I have a client/server application that encrypts or decrypts a message both on the client-side and server-side. However on decryption I keep getting the following error from the StackTrace

Input length must be multiple of 8 when decrypting with padded cipher

Following is the code from both the Server and Client classes. The thing is I have tried using ("DES/CBC/PKCS5Padding") and ("UTF-8") but still haven't been able to fix said issue. Any help would be appreciated thanks?

public class ServerApp   {

    public static byte[] encrypt(String input, Key k) {
        try {

            Cipher cipher = Cipher.getInstance("DES");
            cipher.init(Cipher.ENCRYPT_MODE, k);
            byte[] data = input.getBytes();
            byte[] result = cipher.doFinal(data);

            return result;
        } catch (Exception ex) {
            return null;
        }
    }

    public static String decrypt(byte[] cipher, Key k) {
        try {

            Cipher cipher1 = Cipher.getInstance("DES");
            cipher1.init(Cipher.DECRYPT_MODE, k);
            byte[] original = cipher1.doFinal(cipher);
            return new String(original);

        } catch (Exception ex) {
            return null;
            //Logger.getLogger(DES.class.getName()).log(Level.SEVERE, null, ex);
        }
    }

    public static void main(String[] args) throws NoSuchAlgorithmException {
        try {

              Key key=KeyGen.getSecretKey();
            ServerSocket ser = new ServerSocket(3333);
            System.out.println("Server Started");
            Socket client = ser.accept();
            DataInputStream in = new DataInputStream(client.getInputStream());
            DataOutputStream out = new DataOutputStream(client.getOutputStream());
            Scanner scan = new Scanner(System.in);
           // SecretSocket sc = new SecretSocket(client, KeyGen.getSecretKey());
            String serMsg, cliMsg, plain;
           // OutputStream sout = sc.getOutputStream();
          //  InputStream sin = sc.getInputStream();
            do {
                System.out.print("You say: ");
                serMsg = scan.nextLine();

             //   sout.write(serMsg.getBytes());
            //    System.out.println("cli server "+sin.read());

                byte[] ci = encrypt(serMsg, KeyGen.getSecretKey());
            System.out.println("encrypt " +ci.toString());
             out.writeUTF(ci.toString());
              plain = decrypt(ci, KeyGen.getSecretKey() );
              System.out.println("decrypt " + plain);
            } while (!serMsg.equals("end"));
            client.close();
            ser.close();
        } catch (IOException ex) {
            Logger.getLogger(ServerApp.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
}

public class ClientApp  {

        public static byte[] encrypt(String input, Key k) {
        try {

            Cipher cipher = Cipher.getInstance("DES");
            cipher.init(Cipher.ENCRYPT_MODE, k);
            byte[] data = input.getBytes();
            byte[] result = cipher.doFinal(data);

            return result;
        } catch (Exception ex) {
            return null;
        }
    }

    public static String decrypt(byte[] cipher, Key k) {
        try {

            Cipher cipher1 = Cipher.getInstance("DES/CBC/PKCS5Padding");
            cipher1.init(Cipher.DECRYPT_MODE, k);
            byte[] original = cipher1.doFinal(cipher);
            return new String(original);

        } catch (Exception ex) {
            return null;
            //Logger.getLogger(DES.class.getName()).log(Level.SEVERE, null, ex);
        }
    }

    public static void main(String[] args) throws NoSuchAlgorithmException, InvalidKeyException, NoSuchPaddingException, IllegalBlockSizeException, BadPaddingException {
        try {
            Socket s = new Socket("localhost", 3333);
            DataInputStream in = new DataInputStream(s.getInputStream());
            DataOutputStream out = new DataOutputStream(s.getOutputStream());
            Scanner scan = new Scanner(System.in);
            String serMsg, cliMsg, plain;

            do {

                System.out.println("server server "+in.readUTF());

                serMsg = in.readUTF();
                System.out.println("enc: " + serMsg);
                plain = decrypt(serMsg.getBytes("UTF-8"), KeyGen.getSecretKey());
                System.out.println("Server says: " + plain);

            } while (!serMsg.equals("end"));
            s.close();
        } catch (IOException ex) {
            Logger.getLogger(ClientApp.class.getName()).log(Level.SEVERE, null, ex);
        }
    }

Answer 1

        Cipher cipher = Cipher.getInstance("DES");
        cipher.init(Cipher.ENCRYPT_MODE, k);
        byte[] data = input.getBytes();
        byte[] result = cipher.doFinal(data);

1. Using DES without IV you are implicitly using DES/ECB/PKCS5Padding.

2. do not print a byte array directly. Java will output only printable characters. Always encode and decode a byte array when printing (Hex or Base64 are the most common encodings)

Here is an example project

Base64.getEncoder().encodeToString(byteArray) 

3. I hope you are aware DES is considered a weak cipher today and should be used only for backward compatibility.