import java.io.ByteArrayOutputStream;  import java.io.File;  import java.io.FileInputStream;  import java.io.FileNotFoundException;  import java.io.FileOutputStream;  import java.io.IOException;  import java.io.ObjectInputStream;  import java.io.ObjectOutputStream;  import java.security.Key;  import java.security.KeyPair;  import java.security.KeyPairGenerator;  import javax.crypto.Cipher;    /**   * 公钥加密，私钥解密(非对称加密)   *    */  public class AsymmetricEncryption {        public static void main(String[] args) throws Exception {          publicEnrypy();          privateEncode();      }        /**       * 加密的方法,使用公钥进行加密       * @throws Exception       */      public static void publicEnrypy() throws Exception {            Cipher cipher = Cipher.getInstance("RSA");            KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");            // 生成钥匙对          KeyPair keyPair = keyPairGenerator.generateKeyPair();            // 得到公钥          Key publicKey = keyPair.getPublic();            // 得到私钥          Key privateKey = keyPair.getPrivate();            // 设置为加密模式          cipher.init(Cipher.ENCRYPT_MODE, publicKey);            // 对数据进行加密          byte[] result = cipher.doFinal("aaa".getBytes());            //把私钥保存到硬盘上          saveKey(privateKey);            //把加密后的数据保存到硬盘上          saveData(result);      }        /**       * 解密的方法，使用私钥进行解密       * @throws Exception       */      public static void privateEncode() throws Exception {          Cipher cipher = Cipher.getInstance("RSA");            // 从硬盘中读取私钥          Key privateKey = loadKey();            //设置为解密模式，用私钥解密          cipher.init(Cipher.DECRYPT_MODE, privateKey);            // 从硬盘中读取加密后的数据          byte[] data = loadData();            //对加密后的数据进行解密，返回解密后的结果          byte[] result = cipher.doFinal(data);            System.out.println(new String(result));      }        /**       * 从硬盘中加载加密后的文件       * @return       * @throws FileNotFoundException       * @throws IOException       */      private static byte[] loadData() throws FileNotFoundException, IOException {          FileInputStream fileInputStream = new FileInputStream(new File(                  "E://data.data"));          ByteArrayOutputStream outputStream = new ByteArrayOutputStream();            byte[] buffer = new byte[1024];          int len = 0;            while ((len = fileInputStream.read(buffer)) != -1) {              outputStream.write(buffer, 0, len);          }            fileInputStream.close();            return outputStream.toByteArray();      }        /**       * 从硬盘中加载私钥       * @return       * @throws IOException       * @throws FileNotFoundException       * @throws ClassNotFoundException       */      private static Key loadKey() throws IOException, FileNotFoundException,              ClassNotFoundException {          ObjectInputStream inputStream = new ObjectInputStream(                  new FileInputStream(new File("E://private_key")));          Key privateKey = (Key) inputStream.readObject();          return privateKey;      }        /**       * 把加密后的密文保存到硬盘上       * @param result       * @throws FileNotFoundException       * @throws IOException       */      private static void saveData(byte[] result) throws FileNotFoundException,              IOException {          FileOutputStream fileOutputStream = new FileOutputStream(new File(                  "E://data.data"));          fileOutputStream.write(result);      }        /**       * 把私钥保存到硬盘上       * @param privateKey       * @throws IOException       * @throws FileNotFoundException       */      private static void saveKey(Key privateKey) throws IOException,              FileNotFoundException {          ObjectOutputStream outputStream = new ObjectOutputStream(                  new FileOutputStream(new File("E://private_key")));          outputStream.writeObject(privateKey);      }    }