java 加密之RSA算法加密与解密的实例详解

 private static final String ALGORITHM = "RSA";
 private static final String PRIVATE_KEY_PATH = "D:\\rsa_private.isa";
 private static final String PUBLIC_KEY_PATH = "D:\\rsa_public.isa";
 
 /**
 * 生成公钥和私钥并存储到文件中
 * @throws Exception
 */
 @Test
 public void geneKeyPair() throws Exception {
 KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(ALGORITHM);
 keyPairGenerator.initialize(1024);
 KeyPair keyPair = keyPairGenerator.generateKeyPair();
 PrivateKey privateKey = keyPair.getPrivate();//私钥
 PublicKey publicKey = keyPair.getPublic();//公钥
 byte[] privateKeyBytes = privateKey.getEncoded();//私钥对应的字节数组
 byte[] publicKeyBytes = publicKey.getEncoded();//公钥对应的字节数组
 Files.write(Paths.get(PRIVATE_KEY_PATH), privateKeyBytes);
 Files.write(Paths.get(PUBLIC_KEY_PATH), publicKeyBytes);
 }

@Test
 public void testEncrypt() throws Exception {
 this.encrypt("Hello RSA");
 }
 
 /**
 * 公钥加密
 * @param value
 * @return
 * @throws Exception
 */
 private byte[] encrypt(String value) throws Exception {
 Cipher cipher = Cipher.getInstance(ALGORITHM);
 //读取公钥对应的字节数组
 byte[] publicKeyCode = Files.readAllBytes(Paths.get(PUBLIC_KEY_PATH));
 //构造公钥，存储起来的公钥需要使用X509EncodedKeySpec进行读取
 X509EncodedKeySpec keySpec = new X509EncodedKeySpec(publicKeyCode);
 KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);
 //根据已有的KeySpec生成对应的公钥
 PublicKey publicKey = keyFactory.generatePublic(keySpec);
 cipher.init(Cipher.ENCRYPT_MODE, publicKey);
 byte[] result = cipher.doFinal(value.getBytes());
 System.out.println(Base64.getEncoder().encodeToString(result));
 return result;
 }

 /**
 * 私钥解密
 * @throws Exception
 */
 @Test
 public void testDecrypt() throws Exception {
 Cipher cipher = Cipher.getInstance(ALGORITHM);
 byte[] privateKeyCode = Files.readAllBytes(Paths.get(PRIVATE_KEY_PATH));
 //私钥需要通过PKCS8EncodedKeySpec来读取
 PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(privateKeyCode);
 KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);
 //生成私钥
 PrivateKey privateKey = keyFactory.generatePrivate(keySpec);
 cipher.init(Cipher.DECRYPT_MODE, privateKey);
 String content = "Java Program";
 byte[] input = this.encrypt("Java Program");
 byte[] result = cipher.doFinal(input);
 Assert.assertTrue(content.equals(new String(result)));
 }