[实验任务]：加密算法

目前常用的加密算法有DES（Data Encryption Standard）和IDEA（International Data Encryption Algorithm）国际数据加密算法等，请用工厂方法实现加密算法系统。

public interface Encryption
{
    String encrypt(String text);

    String decrypt(String ciphertext);
}

public class DES implements Encryption
{
    private SecretKey secretKey;

    public DES()
    {
        try
        {
            KeyGenerator keyGenerator = KeyGenerator.getInstance("DES");
            secretKey = keyGenerator.generateKey();
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
    }

    //DES加密
    @Override
    public String encrypt(String text)
    {
        try
        {
            Cipher cipher = Cipher.getInstance("DES");
            cipher.init(Cipher.ENCRYPT_MODE, secretKey);
            byte[] encryptedBytes = cipher.doFinal(text.getBytes(StandardCharsets.UTF_8));
            return Base64.getEncoder().encodeToString(encryptedBytes);
        }
        catch (Exception e)
        {
            e.printStackTrace();
            return null;
        }
    }

    //DES解密
    @Override
    public String decrypt(String ciphertext)
    {
        try
        {
            Cipher cipher = Cipher.getInstance("DES");
            cipher.init(Cipher.DECRYPT_MODE, secretKey);
            byte[] decryptedBytes = cipher.doFinal(Base64.getDecoder().decode(ciphertext));
            return new String(decryptedBytes, StandardCharsets.UTF_8);
        }
        catch (Exception e)
        {
            e.printStackTrace();
            return null;
        }
    }
}

public class IDEA implements Encryption
{
    private SecretKey secretKey;

    static
    {
        // 添加Bouncy Castle提供程序
        Security.addProvider(new BouncyCastleProvider());
    }

    public IDEA()
    {
        try
        {
            KeyGenerator keyGenerator = KeyGenerator.getInstance("IDEA", "BC");
            secretKey = keyGenerator.generateKey();
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
    }

    @Override
    public String encrypt(String text)
    {
        try
        {
            // 创建一个IDEA加密器
            Cipher cipher = Cipher.getInstance("IDEA/ECB/PKCS5Padding", "BC");
            cipher.init(Cipher.ENCRYPT_MODE, secretKey);
            byte[] encryptedBytes = cipher.doFinal(text.getBytes());
            return Base64.getEncoder().encodeToString(encryptedBytes);
        }
        catch (Exception e)
        {
            e.printStackTrace();
            return null;
        }
    }

    @Override
    public String decrypt(String ciphertext)
    {
        try
        {
            Cipher cipher = Cipher.getInstance("IDEA/ECB/PKCS5Padding", "BC");
            cipher.init(Cipher.DECRYPT_MODE, secretKey);
            byte[] encryptedBytes = Base64.getDecoder().decode(ciphertext);
            return new String(cipher.doFinal(encryptedBytes), StandardCharsets.UTF_8);
        }
        catch (Exception e)
        {
            e.printStackTrace();
            return null;
        }
    }
}

public interface EncryptionFactory
{
    Encryption createEncryption();
}

public class DESFactory implements EncryptionFactory
{
    @Override
    public Encryption createEncryption()
    {
        return new DES();
    }
}

public class IDEAFactory implements EncryptionFactory
{
    @Override
    public Encryption createEncryption()
    {
        return new IDEA();
    }
}

import java.util.Scanner;

public class FactoryMethod
{
    public static void main(String[] args)
    {
        Scanner sc = new Scanner(System.in);
        System.out.println("请输入要加密的文本：");
        String text = sc.next();

        EncryptionFactory factory = null;

        System.out.println("请输入加密算法编号：\n" +
                "1、DES加密  2、IDEA加密");
        int choose = sc.nextInt();
        if (choose == 1)
        {
            //DES加密
            factory = new DESFactory();
            System.out.println("DES加密");
        } else if (choose == 2)
        {
            //IDEA加密
            factory = new IDEAFactory();
            System.out.println("IDEA加密");
        }

        Encryption encryptionAlgorithm = factory.createEncryption();
        String encryptedText = encryptionAlgorithm.encrypt(text);
        String decryptedText = encryptionAlgorithm.decrypt(encryptedText);
        System.out.println("原文本：" + text);
        System.out.println("加密后：" + encryptedText);
        System.out.println("解密后：" + decryptedText);
    }
}

运行结果