/**
* 通過(guò)指定的密鑰長(zhǎng)度生成非對(duì)稱(chēng)的密鑰對(duì)
* @param keySize 推薦使用1024,2048 ，不允許低于1024
* @return
*/
public static KeyPair generateRSAKeyPair(int keySize){
    KeyPair ret = null;
    try {
      //1、準(zhǔn)備生成
      KeyPairGenerator generator = KeyPairGenerator.getInstance("RSA");
      //2、初始化，設(shè)置秘鑰長(zhǎng)度
      generator.initialize(keySize);
      //3、生成，并且返回
      ret = generator.generateKeyPair();
    } catch (NoSuchAlgorithmException e) {
      e.printStackTrace();
    }
    return ret;
}

KeyPair keyPair = EncryptUtil.generateRSAKeyPair(1024);
//獲取公鑰，可以給任何人
PublicKey publicKey = keyPair.getPublic();
 //獲取私鑰
PrivateKey privateKey = keyPair.getPrivate();

/**
* RSA 加密
* @param data 需要加密的數(shù)據(jù)
* @param key 可以是 PublicKey,也可以是PrivateKey
* @return
*/
public static byte[] rsaEncrypt(byte[] data ,Key key){
    byte[] ret = null;
    if (data != null
        && data.length>0
        && key!=null) {
      // 1、創(chuàng)建Cipher 使用RSA
      try {
        Cipher cipher = Cipher.getInstance("RSA");
        //設(shè)置Key
        cipher.init(Cipher.ENCRYPT_MODE,key);
        ret = cipher.doFinal(data);
      } catch (NoSuchAlgorithmException e) {
        e.printStackTrace();
      } catch (NoSuchPaddingException e) {
        e.printStackTrace();
      } catch (InvalidKeyException e) {
        e.printStackTrace();
      } catch (BadPaddingException e) {
        e.printStackTrace();
      } catch (IllegalBlockSizeException e) {
        e.printStackTrace();
      }
    }
    return ret;
}

/**
* RSA 解密
* @param data 要解密的數(shù)據(jù)
* @param key 可以是 PublicKey,也可以是PrivateKey
* @return
*/
public static byte[] rsaDecrypt(byte[] data ,Key key){
    byte[] ret = null;
    if (data != null
        && data.length>0
        && key!=null) {
      // 1、創(chuàng)建Cipher 使用RSA
      try {
        Cipher cipher = Cipher.getInstance("RSA");
        //設(shè)置Key
        cipher.init(Cipher.DECRYPT_MODE,key);
        ret = cipher.doFinal(data);
      } catch (NoSuchAlgorithmException e) {
        e.printStackTrace();
      } catch (NoSuchPaddingException e) {
        e.printStackTrace();
      } catch (InvalidKeyException e) {
        e.printStackTrace();
      } catch (BadPaddingException e) {
        e.printStackTrace();
      } catch (IllegalBlockSizeException e) {
        e.printStackTrace();
      }
    }
    return ret;
}

//獲得公鑰 私鑰
PrivateKey privateKey = keyPair.getPrivate();
PublicKey publicKey = keyPair.getPublic();
//編碼將PublicKey和PrivateKey對(duì)象轉(zhuǎn)換為字節(jié)數(shù)組，該字節(jié)數(shù)組為公鑰、私鑰的實(shí)際數(shù)據(jù)
byte[] publicKeyEncoded = publicKey.getEncoded();
byte[] privateKeyEncoded = privateKey.getEncoded();
//將字節(jié)數(shù)組通過(guò)Base64編碼算法 編碼成可見(jiàn)的字符形式
String publickey = Base64.encodeToString(publicKeyEncoded, Base64.NO_WRAP);
String privatekey = Base64.encodeToString(privateKeyEncoded, Base64.NO_WRAP);
//進(jìn)行存儲(chǔ)操作
 。。。。

//獲取公鑰
//str_publickey 為公鑰字符串形式數(shù)據(jù)（公鑰先編碼成byte[] 在 形成字符串）
//解碼
byte[] publicdecode = Base64.decode(new String(str_publickey), Base64.NO_WRAP);
//構(gòu)造X509EncodedKeySpec對(duì)象
X509EncodedKeySpec publicKeySpec = new X509EncodedKeySpec(publicdecode);
//指定加密算法
KeyFactory keyFactory = KeyFactory.getInstance("RSA");
//取得公鑰
PublicKey publicKey = keyFactory.generatePublic(publicKeySpec);
//解碼
//獲取私鑰
//str_private 為私鑰字符串形式的數(shù)據(jù)
byte[] privatedecode = Base64.decode(new String(str_private), Base64.NO_WRAP);
//構(gòu)造X509EncodedKeySpec對(duì)象
PKCS8EncodedKeySpec privateKeySpec = new PKCS8EncodedKeySpec(privatedecode);
//指定加密算法
keyFactory = KeyFactory.getInstance("RSA");
//取得私鑰
PrivateKey privateKey = keyFactory.generatePrivate(privateKeySpec);