package com.test.rsa;    import java.io.ByteArrayOutputStream;  import java.io.FileInputStream;  import java.io.FileOutputStream;  import java.io.ObjectInputStream;  import java.io.ObjectOutputStream;  import java.security.KeyPair;  import java.security.KeyPairGenerator;  import java.security.NoSuchAlgorithmException;  import java.security.PrivateKey;  import java.security.PublicKey;  import java.security.SecureRandom;    import javax.crypto.Cipher;    public class RSAUtil {     /**    * 加密    */   public static byte[] encrypt(PublicKey pk, byte[] data) throws Exception {    try {     Cipher cipher = Cipher.getInstance("RSA", new org.bouncycastle.jce.provider.BouncyCastleProvider());     cipher.init(Cipher.ENCRYPT_MODE, pk);     int blockSize = cipher.getBlockSize();// 获得加密块大小，如：加密前数据为128个byte，而key_size=1024     // 加密块大小为127     // byte,加密后为128个byte;因此共有2个加密块，第一个127     // byte第二个为1个byte     int outputSize = cipher.getOutputSize(data.length);// 获得加密块加密后块大小     int leavedSize = data.length % blockSize;     int blocksSize = leavedSize != 0 ? data.length / blockSize + 1 : data.length / blockSize;     byte[] raw = new byte[outputSize * blocksSize];     int i = 0;     while (data.length - i * blockSize > 0) {      if (data.length - i * blockSize > blockSize)       cipher.doFinal(data, i * blockSize, blockSize, raw, i * outputSize);      else       cipher.doFinal(data, i * blockSize, data.length - i * blockSize, raw, i * outputSize);      // 这里面doUpdate方法不可用，查看源代码后发现每次doUpdate后并没有什么实际动作除了把byte[]放到      // ByteArrayOutputStream中，而最后doFinal的时候才将所有的byte[]进行加密，可是到了此时加密块大小很可能已经超出了      // OutputSize所以只好用dofinal方法。         i++;     }     return raw;    } catch (Exception e) {     throw new Exception(e.getMessage());    }   }      /**    * 解密    */   public static byte[] decrypt(PrivateKey pk, byte[] raw) throws Exception {    try {     Cipher cipher = Cipher.getInstance("RSA", new org.bouncycastle.jce.provider.BouncyCastleProvider());     cipher.init(cipher.DECRYPT_MODE, pk);     int blockSize = cipher.getBlockSize();     ByteArrayOutputStream bout = new ByteArrayOutputStream(64);     int j = 0;        while (raw.length - j * blockSize > 0) {      bout.write(cipher.doFinal(raw, j * blockSize, blockSize));      j++;     }     return bout.toByteArray();    } catch (Exception e) {     throw new Exception(e.getMessage());    }   }      /**    *     * 根据本地的RSAKey文件获取KeyPair    *     * @throws Exception    */   public static KeyPair getKeyPair(String rsaKeyStore) throws Exception {    FileInputStream fis = new FileInputStream(rsaKeyStore);    ObjectInputStream oos = new ObjectInputStream(fis);    KeyPair kp = (KeyPair) oos.readObject();    oos.close();    fis.close();    return kp;   }      /**    *     * 存储KeyPair到本地    *     * @throws Exception    */   public static void saveKeyPair(KeyPair kp, String path) throws Exception {    FileOutputStream fos = new FileOutputStream(path);    ObjectOutputStream oos = new ObjectOutputStream(fos);    // 生成密钥    oos.writeObject(kp);    oos.close();    fos.close();   }      /**    *     * 用于生成公匙或私匙    *     * @throws NoSuchAlgorithmException    *     */   public static KeyPair generateKeyPair() throws NoSuchAlgorithmException {       SecureRandom sr = new SecureRandom();    KeyPairGenerator kg = KeyPairGenerator.getInstance("RSA", new org.bouncycastle.jce.provider.BouncyCastleProvider());    // 注意密钥大小最好为1024,否则解密会有乱码情况.    kg.initialize(1024, sr);    KeyPair genKeyPair = kg.genKeyPair();    return genKeyPair;      }      /**    *     * 测试    *     */   public static void main(String[] args) throws Exception {       // 获取公匙及私匙    KeyPair generateKeyPair = getKeyPair("E:\\code\\key");    //生成公钥及私钥    //KeyPair generateKeyPair = generateKeyPair();       // 公匙 用于前台加密    PublicKey publicKey = generateKeyPair.getPublic();    System.out.println(publicKey);       // 私匙 存储在后台用于解密    PrivateKey privateKey = generateKeyPair.getPrivate();    System.out.println(privateKey);       // 存储KeyPair到本地用于后期解密 注意修改前台RSAKeyPair    //saveKeyPair(generateKeyPair,"E:\\code\\key");       // 测试加密解密    String test = "saaaa";    // test = "阿斯顿发送对发生地发送盗伐水电费圣达菲sadfsadf爱上对方爱上对方";           byte[] en_test = encrypt(publicKey, test.getBytes());    System.out.println("加密后字符:" + new String(en_test));       byte[] de_test = decrypt(privateKey, en_test);    System.out.println("解密后字符:" + new String(de_test));      }     }