How to implement DES encryption algorithm using java

How to use Java to implement the DES encryption algorithm

Overview:
DES (Data Encryption Standard) is a symmetric encryption algorithm that is widely used in data in the computer field Encrypting and decrypting. In Java, we can use the javax.crypto library to implement the DES encryption algorithm.

Steps:

1. Import related libraries
   First, you need to import the relevant classes in the javax.crypto library. Add the following import statements at the beginning of your code:

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax. crypto.spec.SecretKeySpec;

2. Generate key
   The DES algorithm uses an 8-byte key, and we can use the KeyGenerator class to generate the key. The following is a code example to generate a key:

KeyGenerator keyGenerator = KeyGenerator.getInstance("DES");
SecretKey secretKey = keyGenerator.generateKey();
byte[] keyBytes = secretKey.getEncoded();

3. Convert the key
   The generated key is an object of SecretKey type, and we need to convert it to an object of SecretKeySpec type for use. The following is a code example for converting a key:

SecretKeySpec secretKeySpec = new SecretKeySpec(keyBytes, "DES");

4. Creating an encryption instance
   Using the Cipher class can To create an encryption instance, we use the DES/CBC/PKCS5Padding algorithm mode for encryption. The following is a code example to create an encryption instance:

Cipher cipher = Cipher.getInstance("DES/CBC/PKCS5Padding");

5. Initialize the encryption instance
   Initialization When encrypting an instance, you need to specify the encryption mode, key, and initialization vector (IV). Then call the init method of cipher for initialization. The following is a code example to initialize an encryption instance:

// Get the initialization vector
byte[] iv = new byte[cipher.getBlockSize()];
SecureRandom secureRandom = new SecureRandom( );
secureRandom.nextBytes(iv);

cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec, new IvParameterSpec(iv));

6. Encrypted data
   Use The doFinal method of cipher can encrypt data. The following is a code example to encrypt data:

byte[] encryptedBytes = cipher.doFinal(input.getBytes());

7. Decrypt data
   Decrypt The steps for data encryption are similar. You only need to change the encryption mode to decryption mode. The following is a code example to decrypt data:

cipher.init(Cipher.DECRYPT_MODE, secretKeySpec, new IvParameterSpec(iv));

byte[] decryptedBytes = cipher.doFinal(encryptedBytes );

8. Full sample code:

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey ;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.security.SecureRandom;

public class DESExample {

public static void main(String[] args) throws Exception {
    // 生成密钥
    KeyGenerator keyGenerator = KeyGenerator.getInstance("DES");
    SecretKey secretKey = keyGenerator.generateKey();
    byte[] keyBytes = secretKey.getEncoded();

    // 转换密钥
    SecretKeySpec secretKeySpec = new SecretKeySpec(keyBytes, "DES");

    // 创建加密实例
    Cipher cipher = Cipher.getInstance("DES/CBC/PKCS5Padding");

    // 初始化加密实例
    byte[] iv = new byte[cipher.getBlockSize()];
    SecureRandom secureRandom = new SecureRandom();
    secureRandom.nextBytes(iv);

    cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec, new IvParameterSpec(iv));

    // 加密数据
    String input = "Hello, world!";
    byte[] encryptedBytes = cipher.doFinal(input.getBytes());

    // 解密数据
    cipher.init(Cipher.DECRYPT_MODE, secretKeySpec, new IvParameterSpec(iv));

    byte[] decryptedBytes = cipher.doFinal(encryptedBytes);

    // 打印结果
    System.out.println("明文：" + input);
    System.out.println("加密后：" + new String(encryptedBytes));
    System.out.println("解密后：" + new String(decryptedBytes));
}

}

Summary:
Through the above steps, we can use Java to implement the DES encryption algorithm. In actual development, you can make reasonable selections of encryption algorithms and encryption modes according to your own needs, and make appropriate adjustments according to specific business scenarios. However, please note that the DES encryption algorithm is obsolete and is no longer recommended. A more secure option is the AES encryption algorithm.

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