java加密算法怎么应用

Java中常用的加密算法有DES、AES、RSA等。以下是这些算法的应用示例：

1. DES加密算法的应用示例：

import javax.crypto.*; import javax.crypto.spec.DESKeySpec; import javax.crypto.spec.SecretKeySpec; import java.security.InvalidKeyException; import java.security.Key; import java.security.NoSuchAlgorithmException; import java.security.spec.InvalidKeySpecException;  public class DESExample {     public static void main(String[] args) throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, InvalidKeySpecException, BadPaddingException, IllegalBlockSizeException {         String plaintext = "Hello, world!";         String keyString = "mysecretkey"; // 密钥，长度必须为8字节          // 生成密钥         SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");         DESKeySpec desKeySpec = new DESKeySpec(keyString.getBytes());         SecretKey secretKey = keyFactory.generateSecret(desKeySpec);          // 创建加密器         Cipher cipher = Cipher.getInstance("DES/ECB/PKCS5Padding");         cipher.init(Cipher.ENCRYPT_MODE, secretKey);          // 加密         byte[] encryptedBytes = cipher.doFinal(plaintext.getBytes());         System.out.println("Encrypted: " + new String(encryptedBytes));          // 创建解密器         cipher.init(Cipher.DECRYPT_MODE, secretKey);          // 解密         byte[] decryptedBytes = cipher.doFinal(encryptedBytes);         System.out.println("Decrypted: " + new String(decryptedBytes));     } } 

2. AES加密算法的应用示例：

import javax.crypto.*; import javax.crypto.spec.SecretKeySpec; import java.security.InvalidKeyException; import java.security.Key; import java.security.NoSuchAlgorithmException;  public class AESExample {     public static void main(String[] args) throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, BadPaddingException, IllegalBlockSizeException {         String plaintext = "Hello, world!";         String keyString = "mysecretkey123456"; // 密钥，长度必须为16字节          // 生成密钥         Key key = new SecretKeySpec(keyString.getBytes(), "AES");          // 创建加密器         Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");         cipher.init(Cipher.ENCRYPT_MODE, key);          // 加密         byte[] encryptedBytes = cipher.doFinal(plaintext.getBytes());         System.out.println("Encrypted: " + new String(encryptedBytes));          // 创建解密器         cipher.init(Cipher.DECRYPT_MODE, key);          // 解密         byte[] decryptedBytes = cipher.doFinal(encryptedBytes);         System.out.println("Decrypted: " + new String(decryptedBytes));     } } 

3. RSA加密算法的应用示例：

import javax.crypto.Cipher; import java.nio.charset.StandardCharsets; import java.security.*;  public class RSAExample {     public static void main(String[] args) throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, IllegalBlockSizeException, BadPaddingException {         String plaintext = "Hello, world!";          // 生成密钥对         KeyPairGenerator keyGen = KeyPairGenerator.getInstance("RSA");         keyGen.initialize(2048);         KeyPair keyPair = keyGen.generateKeyPair();         PublicKey publicKey = keyPair.getPublic();         PrivateKey privateKey = keyPair.getPrivate();          // 创建加密器         Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");         cipher.init(Cipher.ENCRYPT_MODE, publicKey);          // 加密         byte[] encryptedBytes = cipher.doFinal(plaintext.getBytes(StandardCharsets.UTF_8));         System.out.println("Encrypted: " + new String(encryptedBytes));          // 创建解密器         cipher.init(Cipher.DECRYPT_MODE, privateKey);          // 解密         byte[] decryptedBytes = cipher.doFinal(encryptedBytes);         System.out.println("Decrypted: " + new String(decryptedBytes));     } } 

以上示例分别演示了DES、AES和RSA加密算法的使用方法，包括生成密钥、创建加密器、加密和解密操作。请注意，密钥的长度必须满足算法要求，否则会抛出异常。加密和解密时使用的密钥必须匹配。