How to use

getPrivateExponent

method

in

java.security.interfaces.RSAPrivateKey

public static String encrypt(byte[] keyBytes, String plainText)
    throws Exception {
  PKCS8EncodedKeySpec spec = new PKCS8EncodedKeySpec(keyBytes);
  KeyFactory factory = KeyFactory.getInstance("RSA", "SunRsaSign");
  PrivateKey privateKey = factory.generatePrivate(spec);
  Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
  try {
    cipher.init(Cipher.ENCRYPT_MODE, privateKey);
  } catch (InvalidKeyException e) {
    //For IBM JDK, 原因请看解密方法中的说明
    RSAPrivateKey rsaPrivateKey = (RSAPrivateKey) privateKey;
    RSAPublicKeySpec publicKeySpec = new RSAPublicKeySpec(rsaPrivateKey.getModulus(), rsaPrivateKey.getPrivateExponent());
    Key fakePublicKey = KeyFactory.getInstance("RSA").generatePublic(publicKeySpec);
    cipher = Cipher.getInstance("RSA");
    cipher.init(Cipher.ENCRYPT_MODE, fakePublicKey);
  }
  byte[] encryptedBytes = cipher.doFinal(plainText.getBytes("UTF-8"));
  String encryptedString = Base64.byteArrayToBase64(encryptedBytes);
  return encryptedString;
}

RawRSAPrivateKey(final RSAPrivateKey original) {
  super(original);
  privateExponent = original.getPrivateExponent();
  modulus = original.getModulus();
}

  boolean isEqual(final RSAPrivateKey key) {
    return super.isEqual(key) && Objects.equals(privateExponent, key.getPrivateExponent()) && Objects.equals(modulus, key.getModulus());
  }
}

private static void test() {
  Pair<RSAPublicKey, RSAPrivateKey> pair = RSAUtils.genKeyPair(RAS_KEY_SIZE);
  //生成公钥和私钥
  RSAPublicKey publicKey = pair.key;
  RSAPrivateKey privateKey = pair.value;
  //模
  String modulus = publicKey.getModulus().toString();
  //公钥指数
  String public_exponent = publicKey.getPublicExponent().toString();
  //私钥指数
  String private_exponent = privateKey.getPrivateExponent().toString();
  //明文
  byte[] ming = "123456789".getBytes(Constants.UTF_8);
  System.out.println("明文：" + new String(ming, Constants.UTF_8));
  //使用模和指数生成公钥和私钥
  RSAPrivateKey priKey = RSAUtils.getPrivateKey(modulus, private_exponent);
  RSAPublicKey pubKey = RSAUtils.getPublicKey(modulus, public_exponent);
  System.out.println("privateKey=" + priKey);
  System.out.println("publicKey=" + pubKey);
  //加密后的密文
  byte[] mi = RSAUtils.encryptByPublicKey(ming, pubKey);
  System.out.println("密文：" + new String(mi, Constants.UTF_8));
  //解密后的明文
  ming = RSAUtils.decryptByPrivateKey(mi, priKey);
  System.out.println("解密：" + new String(ming, Constants.UTF_8));
}

public static String encrypt(byte[] keyBytes, String plainText)
    throws Exception {
  PKCS8EncodedKeySpec spec = new PKCS8EncodedKeySpec(keyBytes);
  KeyFactory factory = KeyFactory.getInstance("RSA", "SunRsaSign");
  PrivateKey privateKey = factory.generatePrivate(spec);
  Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
  try {
    cipher.init(Cipher.ENCRYPT_MODE, privateKey);
  } catch (InvalidKeyException e) {
    //For IBM JDK, 原因请看解密方法中的说明
    RSAPrivateKey rsaPrivateKey = (RSAPrivateKey) privateKey;
    RSAPublicKeySpec publicKeySpec = new RSAPublicKeySpec(rsaPrivateKey.getModulus(), rsaPrivateKey.getPrivateExponent());
    Key fakePublicKey = KeyFactory.getInstance("RSA").generatePublic(publicKeySpec);
    cipher = Cipher.getInstance("RSA");
    cipher.init(Cipher.ENCRYPT_MODE, fakePublicKey);
  }
  byte[] encryptedBytes = cipher.doFinal(plainText.getBytes("UTF-8"));
  String encryptedString = Base64.byteArrayToBase64(encryptedBytes);
  return encryptedString;
}

/**
* Decrypts the specified encrypted Content Encryption Key (CEK).
*
* @param priv         The private RSA key. Must not be {@code null}.
* @param encryptedCEK The encrypted Content Encryption Key (CEK) to
*                     decrypt. Must not be {@code null}.
*
* @return The decrypted Content Encryption Key (CEK).
*
* @throws RuntimeException If decryption failed.
*/
public static SecretKey decryptCEK(final RSAPrivateKey priv,
               final byte[] encryptedCEK)
 throws RuntimeException {
 try {
   RSAEngine engine = new RSAEngine();
   OAEPEncoding cipher = new OAEPEncoding(engine);
   BigInteger mod = priv.getModulus();
   BigInteger exp = priv.getPrivateExponent();
   RSAKeyParameters keyParams = new RSAKeyParameters(true, mod, exp);
   cipher.init(false, keyParams);
   byte[] secretKeyBytes = cipher.processBlock(encryptedCEK, 0, encryptedCEK.length);
   return new SecretKeySpec(secretKeyBytes, "AES");
 } catch (Exception e) {
   // org.bouncycastle.crypto.InvalidCipherTextException
   throw new RuntimeException(Messages.MESSAGES.couldntDecryptCEK(e.getLocalizedMessage()), e);
 }
}

/**
 *  As of 0.9.31, if pk is a RSAPrivateCrtKey,
 *  this will return a RSASigningPrivateCrtKey.
 */
public static SigningPrivateKey fromJavaKey(RSAPrivateKey pk, SigType type)
             throws GeneralSecurityException {
  // private key is modulus (pubkey) + exponent
  BigInteger n = pk.getModulus();
  BigInteger d = pk.getPrivateExponent();
  byte[] b = combine(n, d, type.getPrivkeyLen());
  if (pk instanceof RSAPrivateCrtKey)
    return RSASigningPrivateCrtKey.fromJavaKey((RSAPrivateCrtKey) pk);
  return new SigningPrivateKey(type, b);
}

public static BigInteger extractRSAPrivateExponent(PrivateKey key) throws IOException {
  if (key instanceof RSAPrivateKey) {
    return ((RSAPrivateKey) ((RSAPrivateKey) key)).getPrivateExponent();
  } else {
    return null;
  }
}

public static String toString(Object key) {
  if (key instanceof RSAPrivateKey) {
    RSAPrivateKey pk = (RSAPrivateKey) key;
    return "RSA.Private(" + pk.getModulus() + ":" + pk.getPrivateExponent() + ")";
  }
  if (key instanceof RSAPublicKey) {
    RSAPublicKey pk = (RSAPublicKey) key;
    return "RSA.Private(" + pk.getModulus() + ":" + pk.getPublicExponent() + ")";
  }
  return null;
}

BCRSAPrivateKey(
  RSAPrivateKey key)
{
  this.modulus = key.getModulus();
  this.privateExponent = key.getPrivateExponent();
}

JCERSAPrivateKey(
  RSAPrivateKey key)
{
  this.modulus = key.getModulus();
  this.privateExponent = key.getPrivateExponent();
}

public static String toString(Object key) {
  if (key instanceof RSAPrivateKey) {
    RSAPrivateKey pk = (RSAPrivateKey) key;
    return "RSA.Private(" + pk.getModulus() + ":" + pk.getPrivateExponent() + ")";
  }
  if (key instanceof RSAPublicKey) {
    RSAPublicKey pk = (RSAPublicKey) key;
    return "RSA.Private(" + pk.getModulus() + ":" + pk.getPublicExponent() + ")";
  }
  return null;
}

RawRSAPrivateKey(final RSAPrivateKey original) {
  super(original);
  privateExponent = original.getPrivateExponent();
  modulus = original.getModulus();
}

JCERSAPrivateKey(
  RSAPrivateKey key)
{
  this.modulus = key.getModulus();
  this.privateExponent = key.getPrivateExponent();
}

RawRSAPrivateKey(final RSAPrivateKey original) {
  super(original);
  privateExponent = original.getPrivateExponent();
  modulus = original.getModulus();
}

JCERSAPrivateKey(
  RSAPrivateKey key)
{
  this.modulus = key.getModulus();
  this.privateExponent = key.getPrivateExponent();
}

public static String toString(Object key) {
  if (key instanceof RSAPrivateKey) {
    RSAPrivateKey pk = (RSAPrivateKey) key;
    return "RSA.Private(" + pk.getModulus() + ":" + pk.getPrivateExponent() + ")";
  }
  if (key instanceof RSAPublicKey) {
    RSAPublicKey pk = (RSAPublicKey) key;
    return "RSA.Private(" + pk.getModulus() + ":" + pk.getPublicExponent() + ")";
  }
  return null;
}

RawRSAPrivateKey(final RSAPrivateKey original) {
  super(original);
  privateExponent = original.getPrivateExponent();
  modulus = original.getModulus();
}

public static String toString(Object key) {
  if (key instanceof RSAPrivateKey) {
    RSAPrivateKey pk = (RSAPrivateKey) key;
    return "RSA.Private(" + pk.getModulus() + ":" + pk.getPrivateExponent() + ")";
  }
  if (key instanceof RSAPublicKey) {
    RSAPublicKey pk = (RSAPublicKey) key;
    return "RSA.Private(" + pk.getModulus() + ":" + pk.getPublicExponent() + ")";
  }
  return null;
}

public static RSAKeyParameters generateRSAPrivateKeyParameter(final RSAPrivateKey key) {
  ParamUtil.requireNonNull("key", key);
  if (key instanceof RSAPrivateCrtKey) {
    RSAPrivateCrtKey rsaKey = (RSAPrivateCrtKey) key;
    return new RSAPrivateCrtKeyParameters(rsaKey.getModulus(), rsaKey.getPublicExponent(),
        rsaKey.getPrivateExponent(), rsaKey.getPrimeP(), rsaKey.getPrimeQ(),
        rsaKey.getPrimeExponentP(), rsaKey.getPrimeExponentQ(),
        rsaKey.getCrtCoefficient());
  } else {
    return new RSAKeyParameters(true, key.getModulus(), key.getPrivateExponent());
  }
}