Encryption.java

import java.security.NoSuchAlgorithmException;
import java.security.Security;
import java.util.Base64;
import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;

public class Encryption {

    public static SecretKey generateKey() throws NoSuchAlgorithmException {
        Security.addProvider(new com.sun.crypto.provider.SunJCE());
        KeyGenerator keygen = KeyGenerator.getInstance("DESede");
        keygen.init(168);
        SecretKey klucz = keygen.generateKey();

        return klucz;
    }

    static byte[] encrypt(byte[] plainTextByte, SecretKey klucz)
        throws Exception {
        Cipher cipher = Cipher.getInstance("DESede");
        cipher.init(Cipher.ENCRYPT_MODE, klucz);
        byte[] encryptedBytes = cipher.doFinal(plainTextByte);
        return encryptedBytes;
    }

    static byte[] decrypt(byte[] encryptedBytes, SecretKey klucz)
        throws Exception {
        Cipher cipher = Cipher.getInstance("DESede");
        cipher.init(Cipher.DECRYPT_MODE, klucz);
        byte[] decryptedBytes = cipher.doFinal(encryptedBytes);
        return decryptedBytes;
    }

    public static void main(String[] args) throws Exception {
        SecretKey klucz = generateKey();
        byte[] plainText = "Hello world".getBytes();
        byte[] encrypted = encrypt(plainText, klucz);

        String encodedKey = Base64.getEncoder().encodeToString(klucz.getEncoded());

        byte[] decodedKey = Base64.getDecoder().decode(encodedKey);
        SecretKey klucz2 = new SecretKeySpec(decodedKey, "DESede");

        byte[] decrypted = decrypt(encrypted, klucz2);
        System.out.println("decrypted = " + new String(decrypted));
    }
}