/*******************************************************************************
* Copyright 2009, 2010 Innovation Gate GmbH
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
******************************************************************************/
package de.innovationgate.utils;
import java.io.UnsupportedEncodingException;
import java.security.GeneralSecurityException;
import java.security.Key;
import java.security.KeyFactory;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESKeySpec;
/**
* Util class to encrypt and decrypt data based on RSA keys. As RSA encryption is too slow to encrypt large data we use the following widely accepted method:
* <ul>
* <li> A random DES symmetric key is generated
* <li> data is encrypted using DESEncrypter with the random DES key
* <li> the random DES key ist encrypted with the given RSA Public Key
* </ul>
* <p>
* Note:
* To be able to decrypt the data again the receiver of the encrypted data needs both the DES-ENCRYPTED DATA and the RSA-ENCRYPTED DES KEY!
* </p>
* @deprecated use {@link de.innovationgate.utils.security.RSAEncrypter} instead
*/
public class RSAEncrypter {
private byte[] _desKeyEncryption;
private String _data;
/**
* Encrypt data by the given rsa key. The DES-encrypted data can after that be retrieved by {@link #getData()}. The RSA-encrypted DES key
* used to encrypt the data can then be retrieved from {@link #getDesKeyEncryption()}.
* @param data The data to encrypt
* @param rsaPublicKey The rsa public key used for encryption
* @throws GeneralSecurityException
* @throws UnsupportedEncodingException
*/
public void encrypt(byte[] data, byte[] rsaPublicKey) throws GeneralSecurityException, UnsupportedEncodingException {
// create a tempoary desEncrypter with random desKEY
DESEncrypter desEncrypter = new DESEncrypter();
desEncrypter.init();
X509EncodedKeySpec pubKeySpec = new X509EncodedKeySpec(rsaPublicKey);
KeyFactory keyFactory = KeyFactory.getInstance("RSA");
Cipher ecipher = Cipher.getInstance("RSA");
ecipher.init(Cipher.ENCRYPT_MODE, keyFactory.generatePublic(pubKeySpec));
// encrypt desKey with rsaPubKey
_desKeyEncryption = ecipher.doFinal(desEncrypter.getKey().getEncoded());
// encrypt data with des key
_data = desEncrypter.encrypt(data);
}
/**
* Decrypts the encrypted data string using the given RSA key (to decrypt the DES key) and the DES key (to decrypt the data itself).
* @param data The data to decrypt
* @param rsaPrivateKey The RSA key to decrypt the DES key
* @param desKeyEncryption The RSA-encrypted DES key to decrypt the data
* @return The decrypted data
* @throws GeneralSecurityException
*/
public byte[] decrypt(String data, byte[] rsaPrivateKey, byte[] desKeyEncryption) throws GeneralSecurityException {
// decrypt desKey with rsaPrivateKey
PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(rsaPrivateKey);
KeyFactory keyFactory = KeyFactory.getInstance("RSA");
Key key = keyFactory.generatePrivate(keySpec);
Cipher dcipher = Cipher.getInstance("RSA");
dcipher.init(Cipher.DECRYPT_MODE, key);
byte[] desKeyData = dcipher.doFinal(desKeyEncryption);
DESKeySpec desKeySpec = new DESKeySpec(desKeyData);
SecretKeyFactory desKeyFactory = SecretKeyFactory.getInstance("DES");
SecretKey desKey = desKeyFactory.generateSecret(desKeySpec);
// create desEncrypter with decrypted desKey
DESEncrypter desEncrypter = new DESEncrypter();
desEncrypter.init(desKey);
// decrypt data
return desEncrypter.decrypt(data);
}
/**
* Returns the DES-encrypted data after calling {@link #encrypt(byte[], byte[])}
*/
public String getData() {
return _data;
}
/**
* Returns the RSA-encrypted DES key after calling {@link #encrypt(byte[], byte[])}
*/
public byte[] getDesKeyEncryption() {
return _desKeyEncryption;
}
}